If the Houston Astros hadn't signed Michael Brantley, we probably wouldn't be about to discuss their offense as the best in Major League Baseball history.

But they did, and so here we are.

The Astros are rolling, folks. After a good-not-great April, they've won 11 of 14 and eight in a row in May. Their 29-15 record puts them atop MLB, which is right about where a team that won 204 games across 2017 and 2018 ought to be.

Justin Verlander, Gerrit Cole and the rest of the Astros pitching staff deserve their share of the credit. It does rank second in the American League with a 3.52 ERA, after all.

Yet it's Houston's offense that makes the team go. As of the start of play Thursday, it co-led MLB with 5.6 runs per game and 83 home runs. Meanwhile, it was all alone atop the league with its .282 batting average, .354 on-base percentage and .512 slugging percentage.

To refer to the Astros offense as the best in baseball today would be like referring to the original Jaws as the best of the franchise. There's technically a debate to be had, but...no, not really.

The best offense of all time—now that's a statement and one with strong support.

Consider weighted runs created plus. It's a FanGraphs specialty that quantifies offensive value and adjusts it to allow for comparisons of offensive outputs from different eras. Here's how wRC+ ranks the best offenses in MLB history:

• 1. 2019 Houston Astros: 134 wRC+
• 2. 1927 New York Yankees: 126 wRC+
• T-3. 1930/1931 New York Yankees: 124 wRC+

It's this year's Astros and then three Yankees offenses that were anchored by Babe Ruth and Lou Gehrig.

It's obviously still early, but it's hard not to get excited about an offense that's raking to this degree despite not having the Ruth/Gehrig advantages of limited travel, only seven opponents and a player pool consisting of a single skin color.

Besides, dabbling in making history is nothing new for these Astros. They put up a 122 wRC+ just two years ago, and key contributors to that effort are still around and still producing.

Even despite Jose Altuve's injury-fueled slump, the core foursome of him, George Springer, Alex Bregman and Carlos Correa actually has a higher wRC+ (153) this year than it did in 2017 (144). Josh Reddick had a 128 wRC+ that year and sports a 130 wRC+ so far in 2019.

There are some sketchy performances amid Houston's offensive surge. Robinson Chirinos almost certainly won't maintain a 155 wRC+. Ditto for Jake Marisnick and his 158. And maybe Aledmys Diaz and his 113.

Still, three cracks does not a wavering house of cards make. What matters more is that the core of incumbents in this Astros offense is even stronger than it was two years ago. 

And also, that Brantley has blown away expectations by adding a .329/.379/.575 batting line, 10 home runs and a 157 wRC+ to the middle of Houston's lineup.

If Brantley is the Ringo Starr of this scenario, the Pete Best is Marwin Gonzalez.

Gonzalez was a mainstay for the Astros between 2012 and 2018, and his career offensive peak (highlighted by a 144 wRC+) coincided with the team's epic World Series-winning 2017 campaign. But that was a clear outlier, and the Astros ultimately showed little interest in re-signing him after he entered free agency coming off a modest 104 wRC+ in 2018.

Instead, they maneuvered to fill Gonzalez's shoes in left field with Brantley, who signed a two-year $32 million contract in December.

Brantley's deal looked like a massive bargain even then. Sure, he was a 31-year-old (now 32 as of Wednesday) who'd spent a chunk of his tenure with the Cleveland Indians on the injured list. But he was also a three-time All-Star with a reputation as one of the game's best pure hitters.

Between 2012 and 2018, Brantley racked up a .303/.361/.449 batting line and a 121 wRC+. His chief talent was putting the ball in play. He ranked fifth among all hitters (min. 2,000 plate appearances) with a 9.8 strikeout percentage and second with a 91.2 overall contact percentage.

So far in 2019, Brantley is up to his usual tricks with a 9.9 K% (fourth in MLB) and a 93.0 Contact% (second in MLB). The real difference has been in the power department. His .575 slugging percentage is easily the best of his career, and he's on track to blow away his career best of 20 homers.

A previously middling power hitter suddenly breaking out a Wonderboy is a familiar story in today's MLB. Yet Brantley's is different. His 10.1-degree launch angle is nothing special, and his 88.1 mph exit velocity is his lowest of the Statcast era.

Brantley's improvement is specifically related to how he's hitting fly balls. He's hitting more of them, for one. Secondly, he's hitting them at a lower, yet preferable angle (32.5 degrees) and with more velocity (91.6 mph). Finally, he's keeping them out of center field (34.3 percent), where the big dimensions are.

The result? Try a 459-point increase in his slugging percentage on fly balls compared to 2018.

Why is Brantley doing this? Probably because he can but also because hitting for power is now a greater part of his job description. Houston's Minute Maid Park is a more power-friendly stadium than Cleveland's Progressive Field. Plus, Brantley is batting mostly out of the cleanup spot after hitting there in only 68 games as an Indian.

Only nine players signed for more guaranteed money than Brantley this past winter. Patrick Corbin notwithstanding, those guys have been either just OK or outright disappointing. Bryce Harper and Manny Machado, in particular, have not looked like $330 million and $300 million players, respectively.

Brantley is thus the early leader in the clubhouse for the season's best free-agent signing. And the longer he keeps it up, the longer Houston's offense may remain unlike anything anyone's ever seen.

Stats courtesy of Baseball Reference, FanGraphs and Baseball Savant.