MLB

FRUSTRATION OVER A JOBA NOT-SO-WELL DONE

Joba Chamberlain watched the Yankees’ eighth-inning rally to defeat the Rays yesterday glued to his chair in the clubhouse, too frustrated by his performance to stay on the dugout bench and too superstitious to move during the comeback.

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When the scratching and clawing of his teammates eventually erased the 3-1 deficit for which Chamberlain was on the hook and replaced it with a 4-3 Yankees victory, the pitcher felt a little better.

“It’s a win. That’s all that matters,” said Chamberlain, who was visibly upset when he left the game after six innings in which he allowed five hits and three earned runs, walked one and struck out four.

“I had a terrible sixth,” Chamberlain said. “My fastball command went down the toilet.”

The Rays didn’t do much against Chamberlain for the first five innings, when they amassed one run on two hits. But in the sixth, with the score tied 1-1, Chamberlain allowed three singles and a walk to give the Rays a 3-1 lead. He screamed into his glove as he left the field.

One of Chamberlain’s main goals as a starter is to pitch deep into a game. Being forced from this contest after six innings was the primary source of his frustration.

Chamberlain said he felt no lingering fatigue from his previous start, when he completed eight innings for the first time in his major league career. This time, he was pulled after six because he’d thrown 100 pitches and was struggling with his mechanics.

“My mechanics weren’t very good,” Chamberlain said. “That’s part of the battle, part of trying to get better.”

Chamberlain’s performance was not quite as bad as he’d have people believe, but the 23-year-old is a bit of a perfectionist. That’s a good quality for an athlete to have.

So is having absolute faith in your teammates — the kind of faith Chamberlain has in Mariano Rivera, who blew Saturday’s game. When Rivera took the ball for the ninth yesterday, Chamberlain’s mood lifted. He laughed when asked if he doubted Rivera’s ability to close it out.

“I had no doubt,” said Chamberlain, whose confidence in Rivera is such he was finally able to move off his chair. “I almost went in the shower already [without watching the ninth].”

dtomasino@nypost.com