It was the trade that almost wasn’t (but then was). Just as talks between the Houston Astros and Detroit Tigers over ace pitcher Justin Verlander looked like they were breaking down Thursday, news broke overnight that the two clubs had agreed to terms — Verlander would be headed to Houston after all, as part of a deal that also included cash and prospects.

This is a huge move for the Astros, who needed rotation help ahead of the playoffs. But it might prove to be a big turning point in Verlander’s career, too. Although Verlander has built an impressive résumé in 13 big league seasons, he might not be on a Hall of Fame track quite yet. So what he ends up adding to Houston’s postseason push this season might have an outsize effect on his eventual case for Cooperstown.

Verlander is one of the best pitchers of his generation, of course. He has the fourth-most wins of any active pitcher and the third-most strikeouts. He’s one of only 22 pitchers to win an MVP award, and when he took home the honor in 2011, he was the first in nearly two decades to do it. But according to the advanced metrics — which are taking on more importance in the Hall of Fame voting process with each passing year — Verlander probably still has some work to do before locking down his status as a future Hall member.

According to The Baseball Gauge’s wins above replacement meta-metric, Verlander currently has 53.8 career WAR. The average starting pitcher in Cooperstown has 69.8, so the 34-year-old Verlander would need to tack 16 more WAR onto his lifetime total to reach the typical HOF level. Using a variant of Bill James’s “favorite toy” (which estimates a player’s chances of hitting a statistical milestone given his age and recent track record of production), The Baseball Gauge gives Verlander about a 47 percent chance of putting up the WAR necessary to hit the HOF average. That puts Verlander in a tie for 22nd-highest among active players (and trails fellow pitchers Clayton Kershaw, Zack Greinke, Chris Sale and Max Scherzer) in Hall of Fame probability:

Verlander’s Hall of Fame chances could use some help For active players, probability of matching the average career wins above replacement (WAR) for a Hall of Famer at the same position WAR RK PLAYER POS TEAM CAREER POSITION HOF AVG HOF PROB. 1 Albert Pujols 1B LAA 100.6 66.6 100% 2 Adrian Beltre 3B TEX 80.9 66.4 100 3 Miguel Cabrera 1B DET 66.4 66.6 100 4 Robinson Cano 2B SEA 65.1 69.0 98 5 Joey Votto 1B CIN 54.3 66.6 95 6 Clayton Kershaw SP LAD 57.7 69.8 94 7 Mike Trout CF LAA 50.9 70.3 93 8 Chris Sale SP BOS 36.2 69.8 83 9 Zack Greinke SP ARI 55.6 69.8 81 10 Paul Goldschmidt 1B ARI 35.0 66.6 80 11 Manny Machado 3B BAL 27.5 66.4 80 12 Buster Posey C SF 36.5 57.8 78 13 Kris Bryant 3B CHC 18.7 66.4 73 14 Evan Longoria 3B TB 50.3 66.4 72 15 Nolan Arenado 3B COL 23.5 66.4 64 16 Jose Altuve 2B HOU 25.0 69.0 60 17 Max Scherzer SP WAS 43.0 69.8 58 18 Carlos Correa SS HOU 14.4 67.0 56 19 Mookie Betts RF BOS 18.7 71.2 55 20 Anthony Rizzo 1B CHC 26.0 66.6 55 21 Giancarlo Stanton RF MIA 34.4 71.2 53 22 Bryce Harper RF WAS 25.0 71.2 47 23 Justin Verlander SP DET 53.8 69.8 47 24 Kenley Jansen RP LAD 17.2 37.4 45 25 Andrelton Simmons SS LAA 23.9 67.0 37 WAR in table is a meta-metric that averages together several different versions of the statistic. Numbers accurate as of Friday morning. Source: TheBaseballgauge.com

Hall voters probably won’t be looking only at WAR, which does help Verlander’s case. According to the more conventional indicators included in James’s Black Ink and Hall of Fame Monitor tests (which give more weight to peak performance), Verlander clears the traditional marks necessary for HOF inclusion. But he falls short in the Gray Ink and Hall of Fame Standards tests, which give more weight to long, consistent careers — underscoring just how much Verlander’s Cooperstown case swings depending on which factors you look at.

Verlander’s postseason stats complicate his legacy even further. He’s no stranger to late-October baseball. He led the Tigers on two World Series runs, in 2006 and 2012, but both trips ended abruptly. Verlander was on the losing end of three of the nine games in those series. Aside from dominating sprints through the AL playoffs in 2012 and 2013 (in which he posted a microscopic 0.57 ERA ), Verlander has a 6.00 ERA in the rest of the postseason. So he has run both extremely hot and extremely cold in his playoff career.

But the good news for Verlander is that the Astros will provide him with an opportunity to redeem those up-and-down postseason numbers. Houston has a world-beating offense, and one of its only weaknesses was a rotation that had enjoyed little health and even less consistency throughout most of the season. All due respect to Dallas Keuchel, who has been shaky since returning from injury — but with Verlander, the Astros have picked up a bona fide ace who can anchor the team multiple times in a series and let the big bats go to work.

What makes this trade particularly rare is that players of Verlander’s reputation don’t tend to change addresses midseason, especially not while still producing strong numbers. Out of 1,608 regular-season trades listed on The Baseball Gauge since 1988, only 107 involve a marquee player as accomplished (by wins above replacement ) as Verlander. Swaps involving pitchers are rarer still, and once you consider that the Tigers ace still figures to produce 0.7 WAR over the rest of the season, only 30 trades are comparable to this one.

This isn’t the first time that the Astros have picked up Hall of Fame-caliber pitching talent for the stretch run. In 1998, Houston swapped a trio of young players with the Seattle Mariners for Randy Johnson. Johnson performed admirably as the Astros clinched the division, but Houston lost to the Padres in the NLDS. Johnson would finally get his first (and only) World Series appearance three years later with Arizona.

But the Johnson trade happened at the deadline, while the Verlander deal happened in August, which made this transaction even more unusual. Only 23 players who have been traded as the main piece after the deadline had as much total career value as Verlander; only six were pitchers. Even within that already small pool, half of the players made only minimal contributions to their new teams after the trade.

Given Verlander’s strong performance already this year and Houston’s need atop its rotation, it seems a good bet that Verlander will make much more than a “minimal contribution.” For the sake of both parties’ long-term legacies, they’d better hope so.