Opening Day of the 2019 Major League Baseball season is only a week away, but we're going to skip right past that and look ahead to the summer trade season.

Because teams used to be able to make trades via waivers in August, the July 31 trade "deadline" wasn't actually a deadline. But a new rule eliminated August trades, thereby cementing July 31 as the deadline to make moves. That should result in a greater sense of urgency for teams to sell and buy stars.

We've come to shine a light on 10 stars who could be moved in blockbuster deals this summer. The list mostly consists of pending free agents who might be rented out to contenders. There are also a handful of longer-term assets mixed in.

We'll move roughly in order of each player's likelihood to be moved.

10. David Peralta, Arizona Diamondbacks

The Arizona Diamondbacks are in a strange place going into 2019.

They're coming off a 2018 season that started out well but then devolved into an 82-win flop. Things didn't get much better in the winter, when Arizona traded Paul Goldschmidt and lost Patrick Corbin and A.J. Pollock to free agency.

The D-backs are situated to contend in 2019 anyway, and they just might if enough things break right. If they fall just short, they'll have the pieces to try again in 2020.

The absolute worst-case scenario involves the D-backs pulling a 2018 Baltimore Orioles and plummeting to the bottom of the entire league. In that case, they'd have to put all their trade chips on the table.

In light of Zack Greinke's nigh-immovable $206.5 million contract, the list practically begins with David Peralta. The 31-year-old outfielder is coming off an .868 OPS and 60 extra-base hits (including 30 home runs) in 2018, yet he's set to earn only $7 million in 2019.

Peralta is also under club control through 2020. So if the worst does befall Arizona in 2019, it will have at least one shiny trade chip to cash in.

9. Robbie Ray, Arizona Diamondbacks

Now meet the other shiny trade chip the Diamondbacks might cash in this season. And this one has the potential to be even shinier.

Granted, a couple things will need to happen for Robbie Ray to have peak value on the summer market.

For one, he'll need to avoid further injury trouble after a line drive to the head (not his fault, obviously) and an oblique strain limited him to 52 starts in 2017 and 2018. For two, he'll need to avoid another velocity decrease like the one that held him back at the outset of last season.

But when Ray is right, he's as electric as any pitcher in baseball. To wit, he's struck out 11.8 batters per nine innings since 2016, and he finished 2018 with a 2.65 ERA and 78 strikeouts in 57.2 innings over his last 11 starts.

Furthermore, he is only 27 and earning a modest $6.1 million in his second-to-last season before free agency. He'll thus be a cheap, controllable ace for the D-backs to shop on the summer market should the worst happen to them this season.

8. Aaron Sanchez, Toronto Blue Jays

Unlike the Diamondbacks, the Toronto Blue Jays aren't on a trajectory that might lead to a rebuild. They're already in the middle of one. The only question is how soon it'll be finished.

It probably won't be this season, but the Blue Jays could at least see the light at the end of the tunnel in 2019. All it would take is top prospects Vladimir Guerrero Jr., Bo Bichette and Danny Jansen (who already has the team's catching gig in hand) hitting the ground running.

In that case, the Blue Jays might hold off on trading the assets they control through 2020. That list is notably headlined by right-handers Aaron Sanchez and Marcus Stroman.

If, however, it becomes clear the Blue Jays have more work to do, both should be available this summer. There just might be some complications with Sanchez, who must prove he can stay healthy after finger and hand injuries limited him to 28 starts across 2017 and 2018.

If the 26-year-old were to stay healthy and reclaim his All-Star form of 2016—when he posted an American League-best 3.00 ERA over 192 innings—the Blue Jays will have a young, controllable, top-of-the-rotation starter to cash in.

7. Marcus Stroman, Toronto Blue Jays

Stroman, on the other hand, figures to be as good as gone from the Blue Jays if they don't take a step toward contending in 2019.

To be fair, the 27-year-old righty wants to stick around in Toronto. So he said in February, anyway.

"I want to play here. I've been wanting to play here for a long time. I've been waiting to sign a long-term deal. I've been offered nothing," Stroman told reporters.

Unless, of course, that was a bit of subterfuge on Stroman's part. Perhaps what he was really doing was trying to spur his trade market so he could get the heck out of Toronto.

Whatever the case, Stroman's primary mission for 2019 is putting an injury-marred 2018 behind him so he can pitch more like he did in 2017, when he had a 3.09 ERA over 201 innings. So far, so good. He's looked terrific in posting a 2.19 ERA with 13 strikeouts and one walk in 12.1 spring innings.

Any more of that, and the Blue Jays might eventually market him as a top-of-the-rotation starter who's making only $7.4 million in his penultimate season of club control.

6. Yasiel Puig, Cincinnati Reds

The Cincinnati Reds didn't acquire Yasiel Puig from the Los Angeles Dodgers last December just so they could trade him later.

The 28-year-old right fielder was part of a larger roster overhaul that the Reds are hoping will lead to a worst-to-first season in 2019. Projections by Baseball Prospectus and FanGraphs agree that they should at least avoid a fifth straight season of 90-plus losses.

Trouble is, the NL Central won't make it easy for Cincinnati to rise from the ashes. It's the best division in MLB. And despite their improvements, the Reds are still arguably the worst team in it.

If the Reds are out of the race come July, they won't have any choice but to shop their pending free agents. That includes Puig. He was down and out for a while in 2015 and 2016, but he rose again with an .827 OPS and 51 homers in 2017 and 2018. He's still going strong with a 1.188 OPS this spring.

Throw in how Puig will be earning a less-than-outrageous $9.7 million salary this season, and he'll have a some good value for the Reds to cash in if things go south.

5. Scooter Gennett, Cincinnati Reds

In the same boat as Puig are several other Reds rentals, including Matt Kemp, Tanner Roark, Alex Wood, David Hernandez, Zach Duke and, of course, this guy.

There's been occasional chatter about the Reds possibly signing Scooter Gennett to a contract extension, but he alleges that they've dragged their feet when it comes to actually making something happen.

"[We've] heard absolutely nothing. Zero," he said in February, according to John Fay of the Cincinnati Enquirer.

The 28-year-old was a reclamation project when the Reds snagged him off waivers in 2017. Since then, he's indeed been reclaimed by way of an .859 OPS and 50 homers. Good money is no longer guaranteed on the free-agent market, so he should want to cash in while the getting's good.

If an extension remains out of reach and the Reds do fall out of the race in 2019, Gennett might at least get to play out the final stretch of his walk year in the spotlight with a contender.

Where the Reds are concerned, he could be worth more than Puig on the summer market. He's making slightly more money ($9.8 million), yet the relative scarcity of stars at second base could translate to greater demand for him than for Puig.

4. Jose Abreu, Chicago White Sox

The Chicago White Sox are coming off a 100-loss season, and their attempt to accelerate their rebuild with a big free-agent signing of either Manny Machado or Bryce Harper fell short.

Which is to say, they're a bit more likely than the Reds to be open for business this summer. If they are, the one guy who might be moved in a blockbuster deal is Jose Abreu.

The "might" is necessary in part because the White Sox have never seemed enthused about dealing Abreu. Per Bob Nightengale of USA Today, they apparently still aren't even as he heads into his final season before free agency. That speaks to his value as a veteran presence in their clubhouse.

To boot, he'll only have blockbuster value if he improves on the pedestrian .798 OPS and 22 homers he posted in 2018. Any more of that, and he won't come close to being worth the $16 million salary he's making in 2019.

Before last season, however, the 32-year-old averaged an .883 OPS and 31 homers per season. If he can get back to that, the White Sox will have a middle-of-the-order slugger to rent out to contenders.

3. Nicholas Castellanos, Detroit Tigers

Nicholas Castellanos didn't want to still be with the Detroit Tigers when spring training opened up.

"He wants to win and understands the direction of the franchise right now is to procure prospects," Castellanos' agent, David Meter, said in January, according to Anthony Fenech of the Detroit Free Press. "That being said, he would rather start with his new club going into spring training."

He didn't get his wish. Not because Tigers general manager Al Avila didn't try, but because he did and found that there was "no interest" in the 27-year-old right fielder.

Plenty of teams are set in right field, after all, and the faults in Castellanos' trade value include ugly defensive metrics and a $10 million salary in his final season before free agency.

Castellanos can hit, though. He boasts an .831 OPS dating back to 2016, and his 146 extra-base hits over the last two seasons are tied for ninth. A bat like that would look good in the middle of just about any order.

There's still a question of how much demand will ultimately develop for Castellanos, particularly if he comes to share the market with Puig. But the more time goes on, the more likely it is he'll finally be moved.

2. Will Smith, San Francisco Giants

By the time July rolls around, there's typically so much demand for impact relief pitchers that even rentals can command significant prices on the trade market. 

If anyone is going to further that trend in 2019, it'll be Will Smith.

Though the 29-year-old left-hander is a relative unknown, he's coming off a 2018 season that was highlighted by a 2.55 ERA and 71 strikeouts in 53 innings. And Smith is no LOOGY. Though he's definitely better against lefty batters, he can get righty batters out too.

Smith is going into his final season of club control, in which he'll earn a reasonable $4.2 million. The only way he doesn't get traded is if the San Francisco Giants pull a fast one and reestablish themselves as a contender in the NL West.

This is ostensibly their goal for 2019, but it'll only happen if their many 30-somethings turn back the clock to fitter, happier and more productive times. It's a lot more likely that the Giants will find themselves mired in a third straight losing season, in which case, Smith and others will have to go.

1. Madison Bumgarner, San Francisco Giants

Smith could be the Giants' most valuable lefty rental this summer, but only if Madison Bumgarner fails to put 2017 and 2018 behind him.

He was good enough to put up a 3.29 ERA when he could pitch, yet he was limited to only 38 starts by a dirt bike-induced shoulder injury and line drive-induced broken hand. Besides, his solid ERA obscured a general downfall in his dominance that was clearly linked to diminished fastball velocity.

The 29-year-old has had a positive spring, however. There are the 25 hits he's allowed and the 5.79 ERA he's racked up, but there's also the 18-to-1 strikeout-to-walk ratio in 18.2 innings.

"I've never been in midseason form at the end of spring or to start the year, but I feel like I'm in a good spot to start now," he said Sunday, per Maria Guardado of MLB.com.

If all goes well, Bumgarner's strong spring will springboard him back to what he was between 2011 and 2016, when he averaged a 3.00 ERA and 213 innings per season. His stellar postseason track record is certainly yet another thing that cries, "Ace!"

In this case, his $12 million salary would hardly stand in the way of frenzied trade interest.

Spring stats courtesy of MLB.com. Others courtesy of Baseball Reference and FanGraphs.