As a whole lot of nothing continues to happen during Major League Baseball's lockout, there's no better time to look back on things that might have happened.

So, follow us as we dive into the 10 juiciest "What if?" transactions of the 21st century.

Add up all the signings and trades since 2000 that were rumored but never came to fruition, and there are literally thousands to choose from. Many are compelling on their own, such as when Jacob deGrom could have gone to the Boston Red Sox or when Bryce Harper was nearly a Los Angeles Dodger.

What we were after, though, were deals that truly would have altered the landscape of MLB history if they had been consummated—for the player or the team (or teams) in question, in ways both good and bad.

In lieu of ranking them, we found it easier to simply go in chronological order.

2000: Ken Griffey Jr. to the New York Mets

It was technically in December 1999 that the New York Mets tried to acquire Ken Griffey Jr. from the Seattle Mariners, so not quite the 21st century.

It was certainly with the year 2000 in mind, however, that the Mets were looking to make a splash with the multi-time All-Star, Gold Glover and MVP-winning center fielder. And they came close to finishing a deal, only for Griffey himself to veto it.

In so doing, he left the door open for the Cincinnati Reds to acquire him in February 2000. That worked out better for Seattle than for Cincinnati. Whereas the former scored a real prize in Mike Cameron, the latter found itself saddled with Griffey's injury-laden twilight years.

That is, of course, save for his 2000 campaign. He hit 40 home runs and ranked fourth among center fielders with 5.5 rWAR. It's a shame that he didn't get to do that for the Mets, who went to the World Series in 2000 even in spite of middling production out of center field.

Griffey obviously would have solved that problem and might even have been the key to their avoiding a loss to the crosstown Yankees in the Fall Classic. That would have snapped the Mets' still ongoing championship drought and likewise netted Griffey the ring that otherwise eluded him throughout his 22 big league seasons.

2000: Manny Ramirez to the Seattle Mariners

Speaking of the Mariners, their lineup lost yet another superstar after 2000 when Alex Rodriguez followed Griffey out the door to sign a 10-year, $252 million contract with the Texas Rangers.

This is how the Mariners came to eye Manny Ramirez, then a four-time All-Star and the American League's foremost RBI merchant. So badly did they want him, in fact, that club president Chuck Armstrong even told agent Jeff Moorad that the team would consider moving in Safeco Field's fences to accommodate the slugger.

A kind offer, to be sure. But not as kind as the eight-year, $160 million offer that the Boston Red Sox made to Ramirez, which he accepted. Spoiler for the next slide: That worked out well for both sides.

As for the Mariners, they sort of lucked into getting the big bopper they needed when they subsequently signed Bret Boone. Though he had never before cracked 30 homers or 100 RBI, he went off for 37 and 141 in 2001. 

Ramirez, though, was still a better hitter as he racked up 41 blasts and a 162 OPS+ for Boston. So if the '01 Mariners had signed him instead, they might have made a run at 120 wins in lieu of settling for a mere 116. Who knows? They might also have gotten past the ALCS that year.

2003: Alex Rodriguez to the Boston Red Sox

Just three years into their respective experiments with Rodriguez and Ramirez, the Rangers and Red Sox were about ready to move on. 

Thus came the idea after 2003 to simply swap the two players, plus others, including a young Jon Lester. The catch was that the Red Sox wanted to rework Rodriguez's contract, which had $179 million remaining on it compared to $97.5 million for Ramirez. It was at this that the union balked and squashed the proposed deal.

Heartbreaking for Boston fans in the moment? Undoubtedly. And even more so when A-Rod eventually ended up with the rival Yankees in February 2004.

But then something funny happened. Instead of becoming the latest in a long line of Red Sox tormentors, Rodriguez became the face of the flipping of the script in 2004. It was he who got his face smushed in July, and he who was the butt of a crucial overturned call amid Boston's historic 3-0 comeback in the ALCS.

Though quiet in that series, Ramirez went on to win the MVP for the '04 World Series and to later be a key part of another championship team in 2007. Not to be overlooked, Lester was the winning pitcher in the decisive game of the '07 World Series and the Red Sox's ace when they won another title in 2013.

2007: Miguel Cabrera to the Los Angeles Angels

Miguel Cabrera did a lot of good things for the Florida Marlins, including helping them win the World Series in 2003 and then making four straight All-Star teams.

But since he was getting too expensive for the Marlins' tastes, they traded him to the Detroit Tigers after the 2007 season. That begat a partnership that was all sorts of fruitful, particularly from 2011 to 2014 as Cabrera won two MVPs and the Tigers gathered four straight AL Central titles.

Yet it was Anaheim that Cabrera initially seemed destined for in November '07. The Los Angeles Angels were very serious about acquiring him, to a point where Cabrera later said while visiting Anaheim in 2013, "I thought I would be here."

If the Angels had acquired Cabrera, their playoff-bound teams of 2008 and 2009 would have been centered around one of the best hitters in the American League. They surely needed him in the 2009 ALCS, in which their offense was outclassed by the Yankees.

Had the Angels also extended Cabrera's deal—as the Tigers did—they might have passed on Albert Pujols after 2011. The following year, Cabrera would have become teammates with Mike Trout. As they finished first and second in the AL MVP voting in 2012 and 2013, suffice it to say they would have been quite the power couple.

2008: Barry Bonds to the Tampa Bay Rays

If anyone's going to ask why Barry Bonds didn't keep playing after 2007, there's a perfectly reasonable explanation and potentially more of a nefarious one.

For the former, Bonds' entanglements with performance-enhancing drugs put a scarlet asterisk firmly on his chest. Plus, the '07 season had been his age-42 campaign. Not exactly a prime age for a ballplayer.

And yet Bonds had still posted a .480 OBP and 28 home runs in 2007, so his position that collusion caused him to retire had (and still has) merit. Heck, no team so much as made him an offer for the league minimum.

The Tampa Bay Rays, however, at least had internal discussions about signing Bonds for 2008. Andrew Friedman, then the Rays vice president of baseball operations, called it a "non-story," yet it was easy to see how Bonds fit for what had been the AL's least productive designated hitter spot in 2007.

Had the Rays actually signed Bonds, he would have had the chance to push his career home run total past 762 and closer to 800. He also would have been part of a team that broke out with 97 wins and went to the World Series. With a win there, the ring that he never got in his first 22 seasons would have finally been his.

2010: Zack Greinke to the Washington Nationals

Zack Greinke began his career with some good years for the Kansas City Royals, the peak of which was his Cy Young Award-winning campaign in 2009.

So tired was he of losing, however, that he wanted out after 2010 and got his wish when the Royals shipped him to the Milwaukee Brewers. That led to yet another wish being granted in 2011, in which he was one of several top-notch starters on a 96-win club that fell just two wins shy of going to the World Series.

At that point, Greinke was vindicated in his decision to reject a trade to the Washington Nationals in December 2010. "It wouldn't have gotten as far as it did if it wasn't appealing," he said, but he also noted that he wanted to be with a team that was "looking really good at the moment."

By 2012, though, the Nationals were a 98-win juggernaut powered by excellent pitching. Having Greinke would have given them yet another ace, and thus more depth to withstand Stephen Strasburg's late-season shutdown. That might have been the key to their lasting beyond the first round of the playoffs.

For both Greinke and the Nationals, this is arguably cause to regret not joining forces in 2010. The Royals, on the other hand, have nothing to regret. Their trade with the Brewers brought back Lorenzo Cain and Alcides Escobar, who turned into key players on their World Series teams of 2014 and 2015.

2011: Albert Pujols to the Miami Marlins

As he was the best player in baseball at the time and his newly minted 10-year, $254 million contract was the second-biggest in MLB history, it was a big deal when the Angels signed Pujols in December 2011.

However, the three-time MVP might actually have left money on the table by not joining the Marlins. Though one report only put the team's offer at 10 years, $210 million, another said it was for $275 million over 10 years.

Regardless, it was no great shock to hear that the Marlins were in on Pujols. After having already added Jose Reyes, Mark Buehrle and Heath Bell to a strong core that included Hanley Ramirez and a young Giancarlo Stanton, they were clearly looking ready to make a push for contention.

Would Pujols have put them over the top in 2012? Perhaps not. Yet things might not have gone awry. That year's Marlins lost 93 games, and a fire sale that started with trades of Ramirez and Anibal Sanchez during the summer continued with trades of Reyes, Buehrle and Bell that winter.

If that fire sale was always unavoidable, it's fascinating to look back and wonder what the Pujols trade sweepstakes would have looked like. Because for all his credentials, there were also his red flags as a hugely expensive star whose good-not-great 2012 season hinted at the sharp decline that followed.

2015: Max Scherzer to a 'Mystery Team'

When the Nationals agreed in January 2015 to sign Max Scherzer for $210 million over seven years, even they might not have expected the deal to go as well as it did.

During the life of that contract, Scherzer was a two-time Cy Young Award winner and the most productive pitcher in baseball by rWAR. He was also a crucial part of the Nationals' championship run in 2019, overcoming neck spasms to post a 2.40 ERA in six outings that October.

And yet, it's still worth remembering that there was at least one other team in the bidding for Scherzer before he signed with the Nationals. The twist is that we still don't know which team it was.

There was chatter aplenty of a "mystery team" in the hunt for Scherzer, though various reports nixed possibilities such as the Yankees, Red Sox, Detroit Tigers and the ace's hometown St. Louis Cardinals. This made it easy to cast doubt on the actual existence of a mystery team, but Scherzer himself stood by it.

Of all the speculative possibilities, none is as intriguing as that mystery team being the Toronto Blue Jays. A pursuit of Scherzer would have fit comfortably with their contention timeline, after all, and signing him might have proved to be the boost they needed to get past the ALCS and into the World Series in 2015 and 2016.

2015: Mookie Betts to the Philadelphia Phillies

Going into 2015, the Philadelphia Phillies knew they had to rebuild, and the Red Sox were looking to rebound after their World Series triumph in 2013 was followed swiftly by a last-place finish in 2014.

Since this made the two natural trading partners, it was little wonder when the Red Sox put in an offer for ace left-hander Cole Hamels. Yet that offer didn't include the two players that Ruben Amaro Jr., then the Phillies' general manager, actually wanted.

Those were a pair of prospects, one a catcher named Blake Swihart and the other a second baseman-turned-outfielder named Mookie Betts. The latter was fresh off a promising breakthrough with Boston in 2014, wherein he played 52 games and put up a sturdy 126 OPS+.

Even if it meant never getting Hamels, the Red Sox's refusal to trade Betts proved to be crucial. All he did was turn into one of the game's premier superstars, with his finest work being a 2018 campaign in which he captured the AL MVP and led Boston to a 108-win season and yet another World Series championship.

As for the Phillies, Betts only would have helped them escape the 90-loss purgatory in which they were imprisoned from 2015 to 2017. But if there's a bright side to not doing that trade, it's that already having Betts in right field probably would have made them less inclined to sign Bryce Harper after 2018.

2017: Justin Verlander to the Chicago Cubs

Any trade involving Justin Verlander on the final day of August 2017 was going to need his blessing, and it sounds like it took some convincing to get him to approve a deal to the Houston Astros.

It's not so much that he didn't want to go to Houston as much as he preferred to end up in the National League. Specifically, he wanted to land with the Chicago Cubs, who at the time were the reigning World Series champions.

But while the Cubs also wanted Verlander, then-GM Jed Hoyer later said that the team just wasn't willing to send prospects to the Tigers while also taking on the remainder of Verlander's contract. The 2011 AL MVP and Cy Young Award winner was, after all, owed $56 million through 2019.

Nevertheless, Hoyer came to regret not pursuing Verlander more aggressively. Having him might have made it possible for them to at least get past the Los Angeles Dodgers in the NLCS in 2017, and he could have helped stave off the diminishing returns the team experienced in 2018 and 2019.

As for Verlander and the Astros, well, things worked out just fine for both parties. He dominated with a 2.21 ERA in six outings during Houston's World Series run in 2017 and then went on to finish second and first in the AL Cy Young Award voting for '18 and '19, respectively.

Stats courtesy of Baseball Reference.