a) His track record speaks for itself.
b) Going to a team with a better-than-non-existent chance to win a World Series would amp him up and he would recapture some form of magic that 34-year old pitchers rarely manage to recapture.
Turns out that, so far, both of those points have proven true. He's out-Johnsoning Randy Johnson. Though, to be fair, (and, like Randy Johnson) the Astros didn't acquire Justin Verlander for the regular season.
I don't know how you quantify the fabled Big Game pitcher. Brandon Backe, for example. Roy Oswalt. Roger Clemens (both in Houston and elsewhere). Clayton Kershaw - perhaps the greatest pitcher of our generation - has a 2.36 ERA in the regular season and a 4.55 ERA in the postseason (though his 2015 postseason, 1-1 with a 2.63 ERA) - is maybe not a Big Game pitcher? That just sounds ridiculous, though.
There are numerous sub-plots to what's going on when two starting pitchers face each other. How's the other team's offense? How's your team's offense? What has happened in the games surrounding these starts? So, if you'll allow a fairly simplistic view of this exercise, let's take a look at what happened in the six starts since 2012 that featured Justin Verlander vs. Chris Sale, Boston's likely Game 1 (and, maybe, Game 4/5 starter).
*Note - we'll do this for Justin Verlander and Corey Kluber, should the opportunity present itself.
In six starts, Justin Verlander threw 42IP, 30H/9ER, 44K:9BB when facing the White Sox/Red Sox when Chris Sale started for the other side. This is a 1.93 ERA/0.89 WHIP, with a 4.89 K:BB ratio.
On the other side, Chris Sale threw 42.2IP, 38H/14ER, 48K:12BB when facing the Tigers. This is a 2.95 ERA/1.17 WHIP, and an even 4.00 K:BB ratio.
Game 1
September 2, 2012. 4-2 Detroit win. Verlander, coming off his 2011 Cy Young/AL MVP season, threw 8IP, 4H/1ER, 11K:2BB with the lone run coming on a leadoff Alejandro De Aza home run in the 1st inning. After that home run, Verlander would retire 24 of the next 29 batters, two of whom would reach scoring position. Detroit would go on to win the AL Central with an 88-74 record. He would finish 2nd in AL Cy Young voting to David Price, mainly because Price had 20 wins with Tampa Bay. Price got 14 first-place votes, Verlander got 13.
Sale, whose White Sox would go 85-77 and miss the playoffs, threw 6IP, 6H/4ER, 7K:4BB, and allow two home runs - one to Brennan Boesch, and a three-run shot to Delmon Young in the 6th. 2012 was Sale's 3rd year in the League but his first exclusively out of the rotation, having appeared in 79 games in relief in 2010-2011. Sale would go on to finish the year 17-8 with a 3.05 ERA/1.14 WHIP, and finish 6th in AL Cy Young voting.
Verlander 1
Sale 0
Game 2
September 24, 2014. 2014 was the first season since 2008 that Verlander's ERA (4.54, with a 1.40 WHIP) was above 3.45 for the season and marked the end of five straight All-Star appearances. The 2014 Tigers went 92-70 and won the AL Central again, finishing 17 games ahead of Sale and the White Sox. This game was both of their final starts of the regular season. Verlander would throw 8IP for the first time in nine starts, allowing 7H/1ER, 6K:0BB, the 4th time all season that he would allow 0 or 1 earned runs.
Sale threw 6IP, 4H/1ER, 10K:3BB, wrapping up a season in which he went 12-4 with a 2.17 ERA/0.97 WHIP. His 173 ERA+ led the AL and he was two seasons deep into what will likely be a 6-year streak of finishing in the Top 5 in AL Cy Young voting. That September 24 game - a 6-1 Tigers win after Javy Guerra and former Astros great Matt Lindstrom combined to allow 5ER in 1.2IP - was Sale's 7th Quality Start in his previous eight outings.
Verlander 1
Sale 1
Game 3
August 31, 2016. Detroit and Chicago would both miss the playoffs - the Tigers by three games and the White Sox by eleven games. The Tigers would win this game on a walk-off in the bottom of the 9th, but it was a pitcher's duel from the beginning. Verlander threw 7IP, 3H/2ER, 9K:0BB. Both runs came on solo home runs by Jose Abreu (his 19th) and Alex Avila (his 5th). Both came with two outs in the inning. Verlander would finish 2nd in AL Cy Young voting, behind Rick Porcello, though Verlander got 14 1st-place votes to Porcello's eight, and led to this legendary Kate Upton tweet.
Sale, however, threw 8IP, 8H/2ER, 6K:4BB and faced nine more batters (33) than Verlander (24) in this game. Overall, Sale's 2016 season saw him lead the league with six complete games and finish 5th in AL Cy Young voting.
Verlander 2
Sale 1
Game 4
The next time through the rotation, September 5, saw a rematch of Verlander-Sale. Detroit would in 5-3 in 11 innings, but saw another classic match-up between two of the AL's best pitchers. Verlander would throw 7IP, 8H/2ER, 11K:1BB with a solo home run allowed. Sale threw 8IP, 6H/2ER, 8K:0BB with two solo home runs allowed.
Verlander 2
Sale 2
Game 5
Which brings us to 2017. Verlander's issues early on in 2017 are well-documented. But, like most pitchers, a few key bad outings can really screw up the dashboard stats: 9ER against Cleveland on April 15. Six earned runs at Houston on May 25. Seven more earned runs against Cleveland (wait, this isn't as fun anymore). On July 3 Verlander woke up to a 5-6 record and a 4.96 ERA. Since, then, however, Verlander is 10-3 with a 1.92 ERA/0.86 WHIP, 127K:25BB and a .558 OPS-against. But these struggles happened after Verlander faced Sale and the Red Sox on April 10.
The Tigers won their 6th game of the season 2-1 over Boston. Verlander held the Red Sox to 3H/1R (0ER), 4K:2BB, throwing 67 of 112 pitches for strikes. Sale had himself a game, too, more indicative of his 2017 - it'll be a travesty if he doesn't win the AL Cy Young this year - 7.2IP, 5H/2ER, 10K:1BB, 70 of his 108 pitches for strikes.
Verlander 3
Sale 2
Game 6
Two months later, June 10, saw Boston win 11-3, but eight of those Boston runs came in the 7th-8th innings, after Verlander had left the game. Verlander threw 5IP, 5H/3ER, 3K:4BB, the 5th of six times this season he would walk 4+ batters in an outing. Chris Sale threw 7IP, 9H/3ER, 7K:0BB and hung around long enough to get the win. 82 of his 110 pitches were for strikes.
Verlander 3
Sale 3
So the six matchups are split pretty much down the middle. But Verlander can and will get up for Chris Sale starts. We'll talk about Sale vs the Astros later in the week, but this should be an exciting series, not that that's what any of us want. Verlander is perfectly capable of handling a game when Chris Sale is the other starting pitcher.