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Having an entire arm tested presents a large area for doctors to find trouble. Consequently, Twins closer Glen Perkins was rather uneasy about the process this past week.

When asked about controlling his anxiety level before the exams, the All-Star lefthander said, "The blood pressure test I did before I went through all the tests would probably say no."

Fortunately for Perkins and the Twins, his left elbow is sound. He was found to have some nerve irritation and a muscle strain and has been shut down for the rest of the season, but no surgery is needed.

Now Perkins is mad. There were warning signs in late July that something was wrong. He tried to pitch through it and ended up with several poor September outings that cost his team games.

"I reached personal goals that I wanted to reach, but those are secondary to team goals," he said. "I think the most frustrating thing for me is that, as we started to play better, I started to play worse. And I wasn't happy going out and not getting my job done when everyone else was doing a good job.

"The last one I pitched in, Ricky [Nolasco] goes eight shutout innings [Tuesday against Detroit] and I go give up a three-run homer. We ended up winning the game, which is the ultimate goal, but he didn't get the reward he deserved. His pitching performance in that game goes down the drain.

"[After] Aug. 1 there were a bunch of games that I was a part of that we should have won but we didn't. That's probably the taste I'll have in my mouth during the offseason."

Perkins' problems began July 29 when he picked up a save in Kansas City but gave up a run and a couple of hard hit balls. Perkins has had similar arm problems in the past, but he was able to work through them.

"In 2011, I missed a week," he said. "In 2012, I missed two days. Last year, it was a day here and a day there and it was the same thing this year. There were days where if I thought I needed a day here, a day there, it worked out that I didn't have to pitch those days anyway. It was something where the media didn't find out I was taking a day."

The recent past told Perkins he could work through his problems, but it didn't work this time. He started to have trouble finishing off his trusty slider, and it affected his pitching. He had three blown saves through his first 47 games but four over his next 16. In those 16, he had a 1-2-3 inning only three times.

Opponents reached base against Perkins in each of his final nine appearances, the final one Tuesday, when he gave up a go-ahead, three-run homer to Detroit's J.D. Martinez. It was after that game when Perkins informed the team that his arm was bothering him.

"It gets to the point where I couldn't execute sliders so I tried to stay away from them," he said. "The fastball doesn't have the effectiveness it usually has, and teams probably started to realize that the slider isn't there right now and we're going to look for fastballs."

Perkins gave up 10 earned runs over his last eight appearances.

"I feel bad for him, because he did try to pitch through some things here," Twins General Manager Terry Ryan said. "It was evident the last time or so. Each guy kind of knows what he's supposed to feel like. Sometimes it's pain and sometime it's soreness. Sometimes you get through it, sometimes you can't."

There's a fine line between trying to fight through aches and pains and making an injury worse. Nolasco tried to pitch through an elbow strain, but the results were bad and he eventually landed on the disabled list. Tommy Milone has battled a sore neck all season but has missed his past two starts when it worsened.

Perkins feels bad because he kicked away some games the Twins should have won.

"We just have to do a better job of managing it, and that starts with me," he said. "Not trying to be a tough guy and pitching through it. That's the mentality I'm sure everyone on this team has. You don't want to be in the training room every day, but those guys can help. It's a lesson to learn, from that aspect."