The Astros announced last night that Lance McCullers will take the ball in today’s Game 4 of the ALCS. When asked why he chose McCullers over Brad Peacock, A.J. Hinch responded with a simple answer: “He’s really good.”

McCullers certainly has been really good at times, and he was one of the AL’s best pitchers in the first half of the season, running a 3.05 ERA/2.74 FIP/2.74 xFIP before the All-Star break. But back problems put him on the DL a few times in the second half, and when he did pitch, he wasn’t particularly effective, running an 8.23 ERA/4.29 FIP/4.58 xFIP. At the end of July, I noted that the Astros had a Lance McCullers problem, and they never really got it fixed.

If the Astros were convinced that McCullers was healthy and back to his first-half form, they would have started him in the ALDS. Instead, they went with Peacock as their 4th starter in that series, and used McCullers in relief when that didn’t go well. So why are they showing confidence today in a guy who hasn’t gotten hitters out regularly in several months?

Well, his outing against the Red Sox perhaps provides a clue. The results weren’t overwhelmingly positive — he gave up two runs in three innings, and his high BB%/high BABIP trend from the second half persisted — but in that outing, McCullers simplified his repertoire in a way that might make him a particularly good match-up against the Yankees today.

The most notable thing about McCullers is how often he throws his curveball; no starter threw their curve more often than McCullers during the regular season this year. It’s his primary pitch, and everything else plays off his curve. During the season, he complimented his breaking ball with two kinds of fastballs, both thrown about 20% of the time, and a change-up he’d work in about once every 10 pitches.

McCullers curveball and two-seamer were good pitches for him this year, but his four-seam and his change-up were lousy. By linear weight value, his change-up was one of the worst in baseball this year, and his four-seamer wasn’t much better. When opponents put his four-seamer in play, they ran a .392 wOBA this year, and it was .443 on his change-up. And neither pitch missed bats often enough to justify those results on contact.

So what did Lance McCullers do in his outing against the Red Sox to convince the Astros to give him the ball today? Ditch both the four-seamer and change-up.

In that outing, he threw 49 pitches, 17 of which were two-seamers, and the other 32 of which were curveballs. McCullers decided to go strictly with his two best pitches, and ramp up his curveball usage to another level entirely.

The results don’t show a marked improvement, but McCullers’ missed a ton of bats with his curve as you’d expect, and the Red Sox didn’t really make much in the way of hard contact against him. The average exit velocity on his seven balls in play allowed was just 81.6 mph, and one of the three hits he allowed was a 70 mph dribbler to short that Carlos Correa couldn’t make a play on.

Without his four-seamer and change-up getting whacked around, McCullers was a high-K/high-GB guy who just had to work around the walks he inevitably issued. He mostly did that last week, and the two runs he was charged with came when Chris Devenski relieved him and promptly gave up three straight hits to score both inherited runners.

Knowing he’s likely only out there for three or four innings today, McCullers can likely lean on a very similar strategy, attacking the Yankees line-up with breaking balls. This plan has been mostly obvious against Aaron Judge, who has gone from seeing 33% breaking balls in the regular season to 53% breaking balls in October, but Gary Sanchez has also seen 46% breaking balls in the postseason, and he’s been effectively neutralized by all this curves and sliders from right-handers.

The Yankees line-up is driven heavily by right-handed power, with Brett Gardner, Didi Gregroius, Greg Bird, and Aaron Hicks the only lefties they are starting against McCullers. Gregorius’ postseason home run binge notwithstanding, those aren’t the scary hitters in this New York line-up. And so I would expect that McCullers might again leave his four-seam and his change-up, which are often pitches used to negate the platoon advantage, in the dugout.

Against a line-up of good right-handed power hitters, two-seamers and nasty breaking balls from a right-handed pitcher is a pretty good strategy. And I’d imagine that’s exactly what we’re going to see from McCullers today.

His curve-heavy approach means he’s always going to walk guys, so he might be pitching with guys on base a lot today, but if he can limit the contact quality like he did against Boston by not letting guys get swings against his two worst pitches, McCullers might just be able to give the Astros a good start today. And with Brad Peacock around to bridge the gap to Ken Giles, the Astros have a real chance to win today, and only need one victory from the Justin Verlander/Dallas Keuchel combination they’ll throw the next two days.

The Yankees remain a formidable opponent, but McCullers is a tough match-up for their hitters, and we shouldn’t be surprised if he makes A.J. Hinch look pretty smart a few hours from now.