BOSTON (CBS) — Craig Kimbrel has been a little wild this postseason, leading to some uneasy nights for Red Sox fans.

For that, the Boston closer is sorry.

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Kimbrel made it look relatively easy Thursday night as he locked down Boston’s ALCS-clinching win in Houston, striking out two as he worked a scoreless ninth inning in the 4-1 Red Sox victory. It was the first time this postseason that Kimbrel has not allowed a run.

Kimbrel hasn’t blown a save yet, but he nearly let leads slip away in Games 2 and 4. He also had a cardiac outing in Game 4 against the Yankees in the ALDS, allowing a pair of runs before locking down a 4-3 Boston win to clinch the series.

So even as the champagne flew through the air late Thursday night in the Boston locker room, Kimbrel apologized for all the late-game uncertainty he’s caused over the last few weeks.

“I’m sorry that I gave quite a few of you heart attacks the last few days,” Kimbrel told reporters amid Boston’s celebration. “Let’s hope in the World Series I can make them nice and clean.”

Kimbrel had allowed five runs in 5.1 innings before his clean inning Thursday night. Boston manager Alex Cora said ahead of Game 5 that he thinks his closer has been tipping his pitches.

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“There’s something with his slider, I think,” Cora said. “There has to be something going on because there’s a lot of takes. Quality ones, too. They keep taking it, and that started in New York. Either they have a good game plan or it’s paranoia from my end.”

If that was indeed the issue, Kimbrel made it a point to stay away from his slider in Thursday night’s clincher. All but two of his 14 pitches were fastballs, as he mixed in a pair of knuckle curves. Both of his strikeouts came on four-seemed fastballs.

Kimbrel got Tony Kemp to fly out to Andrew Benintendi to end the game Thursday night, a fitting end to the series following the outfielder’s dynamic game-saving catch at the end of Game 4. Benintendi tried to give Kimbrel the ball after Game 5, but the closer told him to keep it for himself.

“He put it in his back pocket,” Kimbrel told WBZ-TV’s Dan Roche in the locker room.

As for playing in the first Fall Classic of his career, Kimbrel said that feeling will soak in soon enough.

“I know we have a lot more work to do,” he said. “I don’t think it has quite sunk in. I think once we have twice as much media in here we’ll know we’re in the World Series.”

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Boston will play the winner of the Los Angeles Dodgers-Milwaukee Brewers NLCS. Los Angeles leads the series 3-2 with Game 6 Friday night in Milwaukee.