How Houston Astros' Tatsuya Imai tweaked his pitch mix to success in win over Miami Marlins

During his two weeks between starts around the All-Star break, the Houston Astros' pitching coaches met with Tatsuya Imai. Presented were "some changes" for the right-hander to make in the second half, manager Joe Espada said. Pitching coach Josh Miller described the message as more of a reminder.

"Just reminded him of his pitch mix in the NPB last year," Miller said. "How we still think the slider is a special pitch, but he might need some other offerings to help it play up here. And maybe (it would) allow his fastball and his slider to play better if he used some other pitch types more frequently."

The suggestion was not new. In mid-March, during his first Major League Baseball spring training, Imai said through an interpreter he was working to locate his changeup and splitter in the strike zone more often, aiming to "create a little more diversity" with his pitch mix.

That did not manifest, however, in a difficult first half. Imai threw his fastball - four-seam or two-seam - or his slider 94.1% of the time, per Baseball Savant, while compiling a 6.06 ERA over his first 13 starts in MLB and contributing to a Houston rotation ERA that entered Tuesday the second-highest in the sport.

Imai alternated first-half implosions with starts in which he verged on untouchable. He threw six innings of a combined no-hitter and twice logged double-digit strikeouts. Five times, he failed to complete four innings, succumbing to poor command or damage exacted against his two primary pitches.

So, in the meeting, the Astros renewed the call for Imai to incorporate a third pitch, be that the splitter or changeup he threw sporadically in Japan. He totaled 54 of those pitches in the first half. Of those, 15 came in one start against Cleveland, a lineup heavy with left-handed hitters.

"I think I was too focused on the result and … just trying to perform so I wasn't really thinking about the third pitch," Imai said through an interpreter Tuesday night.

Imai's heralded arrival and contract heightened the impetus to perform immediately. Early struggles to adjust to MLB, both on and off the field, are still reflected in the numbers.

"He hasn't felt right, he hasn't felt consistent," Miller said. "He's still searching for feel with all of his pitch mix, even including his slider. There's adjustments when it comes to the opponents you're facing but also the baseball is different, each time he pitches on the road it's a new environment for him. Everything is a little bit different. And we're just trying to catch up and gain comfort and consistency."

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Time to attain it this season is dwindling. Doing so could be vital to the Astros' rotation down the stretch, in what they hope is a playoff race, or at least to Imai's role in it. Barring a freefall by the club, the stakes each time Imai takes the mound the rest of the way will only become higher.

On Tuesday, the enigmatic right-hander forayed into his second half with an effective outing. Imai threw six innings of one-run ball in a 5-3 Astros win that secured a series victory over the Marlins and, with 12 days until the trade deadline, reinforced that rotation improvement might also be found within.

Facing a Marlins offense top-10 in the majors in OPS and batting average, Imai scattered four hits across his six innings, walked three batters and struck out eight. He threw 58% strikes, per Statcast, and coaxed enough swings from the Marlins while showing an openness to the Astros' objective for him.

Imai still relied heavily on his slider, throwing it 54% of the time against a lineup with six left-handed or switch-hitters. But he did mix in 12 changeups or splitters, all to lefties, a modest usage that more than doubled the rate at which he threw those pitches in the first half.

"I thought he got some swing-and-miss on that and it opened the door for the slider and then he (threw) the fastball at 96-97 (mph) to some of them," said Espada. "So I thought the usage of that third pitch was effective for him to be successful."

Imai did not throw a splitter or changeup until his ninth batter, Joe Mack, who fouled off an 0-1 splitter. He did not throw another in the first three innings. But he mixed the changeup more in his second and third times through the order, totaling seven called strikes or whiffs on 11 thrown.

"We're not asking him to use a ton of it," Espada said. "But when he does, it's a good pitch. Now the hitters are, ‘Oh he's using the changeup, so now let's look for it.' And now it opens the door for more areas for him to go and expand the zone."

After totaling 13 changeups in the first half, Imai threw 11 against Miami and said he "felt way better" with the pitch Monday. He landed seven in-zone, four for first-pitch strikes. The Marlins put none into play, taking 27 of 41 swings against his slider. Their 14 balls in play averaged an 87.3 mph exit velocity.

In what Miller deemed pregame "a big start for him," Imai held Miami scoreless until the fifth inning. With two out, he issued a four-pitch walk to Otto Lopez. Kyle Stowers then drove a fastball to the left-center field gap. Lopez sped home on the double to halve a two-run Astros lead.

Heriberto Hernández chased a full-count fastball above the zone, offering Imai a reprieve. After Isaac Paredes made it 5-1 with a three-run homer, Imai returned for the sixth and navigated a walk to Liam Hicks, striking out two batters in the frame, to finish his fifth quality start in 14 outings.

"I wasn't satisfied with the first half of the season," Imai said. "For the last half of the season, I just want to get more ‘W's' and keep performing better."

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