HOUSTON — In the bowels of Minute Maid Park, past the visitors’ clubhouse and down the tunnel leading to the umpires’ locker room, stands the humid, dingy-walled, 900-square-foot cement box where Jackie Bradley Jr. got his groove back.

Red Sox hitting coach Tim Hyers likes to say that batting is infused with insecurity, that “every hitter comes to the ballpark every day searching for his swing.” You can sting a 98-mph fastball off the leftfield wall to score three runs and break a tie, as Bradley did on Sunday, and you can still head into batting practice before the next game praying you can do it again.

Of course, Bradley would never admit he was anxious. Donnie Brittingham, his coach at Prince George (Va.) High School, gave him advice that has stuck with him: “No one should ever know if you’re winning or losing. Keep the same temperament. That way it will allow you to put some perspective into things.” So even when Bradley slumped so badly earlier this season that he was benched for the better part of a week, assistant hitting coach Andy Barkett could only assume he was frustrated. Bradley never showed it. But Barkett knew on Tuesday, before Boston beat the Astros 8–2 in Game 3 of the ALCS, that his 28-year-old centerfielder was not quite right.

“Guys get a little amped-up sometimes [at this time of year],” Barkett said when it was over and the Red Sox were celebrating their 2–1 series lead. “They’re a little jumpy.”

DH J.D. Martinez and rightfielder Mookie Betts like to hit in the second group at batting practice, and they like to spend the first group in the cage with Barkett, listening to music and running through drills. On this day Bradley joined them. Martinez was in and out of the room, but he was in enough to notice that the ball was skipping limply off Bradley’s bat. From his angle, straight on, throwing overhand, Barkett could see only the disease, but from the side, Martinez could see the symptom.

“Oh,” he announced brightly. “You’re too jumpy right now. Control your back side.”

The advice clicked immediately. Bradley focused on keeping his back foot down, on pushing into the ground rather than relying on his momentum to carry him—on being more directional, as Martinez describes it. Everyone in the cage knew he had found it again.

They did not know he would turn on a 94-mph fastball with the bases loaded in the eighth inning and hammer it 386 feet into the rightfield stands.

“It’s huge,” said the understated Bradley of his series-altering home run.

“His teammates loved it,” added first baseman Steve Pearce, who hit his own home run, in the sixth, to break a tie. “I’ll tell you that.”

They were not alone—in the TBS studio, former Red Sox DH David Ortiz ran around screaming and yelling, “Come on, sexy!” and at the Celtics’ home opener, fans started a “JBJ” chant—but in addition to their joy was relief. His teammates knew how trying a season it had been for Bradley. He was hitting .173 and slugging .264 when manager Alex Cora, Hyers and Barkett met with him during a series at Yankee Stadium.

We’re going to sit you while you work on some things, they told him.

OK, said Bradley.

“I’ve had this conversation with many hitters,” Barkett said. “When they’re competing, it’s hard to [make changes]. You’re out there trying to put up results. You can’t relax your brain and chase process when you’re chasing results.” This is going to work, he promised Bradley. And Bradley trusted him.

Around the same time, he was having the same conversation with Martinez, the Red Sox’ unofficial third hitting coach. Martinez had been studying his teammate’s swing, and he noticed that, he said, “it seemed like he could only hit one pitch—the one up.” Bradley knew things weren’t going well, but he didn’t know how to fix them. “These are changes you have to make,” Martinez told him. “If you don’t believe me, I’ll show you everyone else that’s done it.” So they holed up in the video room while Martinez showed him swing after swing of hitters keeping their back foot down, on pushing into the ground rather than relying on their momentum to carry him, on being more directional.

Bradley added a series of drills, including one-handed swings. Plenty of players practice hitting one-handed, but they usually work off the tee or perhaps underhand flips. The Red Sox asked Bradley to take overhand pitches one-handed. It did not go well. He was … “not good at all,” said Barkett. They kept working. These days Bradley lines balls all over the cage one-handed.

“He kept showing up,” said Cora. “He kept working. He kept working his craft. Now you see the results.”

Bradley’s willingness to change was not out of character. As a younger player, he used entire rounds of BP to foul off pitches, so he would know he could spoil good offerings in games, and after his freshman year at Prince George, he spent the summer waiting until he had two strikes before even swinging, to practice his approach in those counts.

“I’m not afraid to fail,” Bradley said Tuesday. “I just don’t want to fail a lot. I want to fail less.”

In the end Bradley sat for six games in eight days. He hit .255 and slugged .451 the rest of the way. There is still work to be done—the double and the home run are his only hits this series—but the ball is flying true.

Bradley said after the double that he enjoys hitting ninth because that slot allows him to be aggressive—“I know they’re not going to pitch around me to get to [Betts]”—and when he hits well, he extends the lineup in a way that wreaks havoc on opponents. Among regulars, no one came to the plate with men on fewer times this year than Betts, the presumptive MVP, with 205. Including home runs, he drove in 80; the average major leaguer under those conditions would have driven in 68.

“Part of controlling the top of their order, which is something that everyone is obsessed with when you face the Red Sox—Betts is good, [leftfielder Andrew] Benintendi, Martinez—if you can control the bottom part of the lineup that's great,” Astros manager A.J. Hinch said Tuesday. “But we haven't. And two games in a row, where Bradley's been in this spot to have the big at bat and he's won of them, it makes them a tougher offense to get through.”

After the game, as they tugged their shirts on in the visitors’ clubhouse, Martinez and Bradley continued talking hitting. “I think the pitch itself helped me stay through,” said Bradley. “It was up.” They discussed mechanics until Bradley was dragged away to his press conference.

Tuesday was a good night. Bradley’s teammates doused him in orange Gatorade after the game, and based on the mood of players as they exited the clubhouse, the celebration seemed likely to continue into the night. But you can bet that Bradley will climb off the team bus on Wednesday and head for the batting cage, where he will search again for his swing.

Stephanie Apstein