Shields seeks answer to post-break breakdown

It was back-to-school day for Scot Shields, who spent a chunk of Monday afternoon studying tapes of his delivery and then reported to the bullpen for a 15-pitch refresher course. His assignment: Iron out the technical glitches that have led to his bloated 8.56 earned-run average since the All-Star break.

“It’s a regular bullpen, nice and easy, to work on things to get back on track, to fix some little mechanical things,” Shields said. “I’m trying to get myself back to normal.”

Normal for Shields is dominant. Considered one of baseball’s best setup men, he had a 1.66 ERA in 41 appearances through July 14.

In 15 games since, he has allowed 13 earned runs in 12 2/3 innings, his ERA jumping to 3.23. Three of those runs came in the eighth inning Friday in Boston, where he gave up a hit and walked two, as the Angels blew a 4-1 lead. Shields was replaced with one out in the inning by Francisco Rodriguez, who gave up back-to-back doubles that produced three runs and a 5-4 Boston lead, but the Angels came back to win, 7-5.

Then came the ultimate indignity Sunday: Shields, who has a 17.65 career ERA in Fenway Park, entered in the eighth with two out, one on and the Angels leading the Red Sox, 3-0.

Shields walked a batter, gave up a run-scoring single to Mike Lowell and was pulled in favor of Justin Speier, who escaped the jam in an eventual 3-1 Angels win.

“That’s the part that [stinks],” Shields said. “I hate it when Frankie and Justin have to come in. That’s my job, and I didn’t do it.”

It was one of those rare moments since 2005 when Manager Mike Scioscia did not believe Shields could get the Angels out of a jam.

“I’m struggling, he made the right move, I totally understand,” Shields said. “But Mike told me [Sunday] night he hasn’t lost confidence in me.”

Still, when the Angels took a 6-4 lead into the eighth inning Monday night against the New York Yankees, Scioscia called on Speier, not Shields. Speier gave up a two-run home run to Jorge Posada that tied the score.

Shields said he has not lost faith in himself. “I’m being aggressive, I have all the confidence in the world,” he said, when asked if his problems were mental. “Physically, I feel as good as I did when I came out of spring training. I’m just not getting results.”

The Angels gained one infielder Monday when Howie Kendrick, out since July 8 because of a fractured left index finger, was activated off the disabled list, but lost another when Erick Aybar was placed on the DL because of a strained left hamstring, suffered while diving for a ball Sunday in Boston.

Kendrick, who started at second base Monday, hopes to avoid the kind of slump he endured after coming off the DL in late May, when he went five for 40 in his first 11 games back, his average falling from .321 to .236.

“The big thing is to pick up where I left off,” he said. “Hopefully, there won’t be too much of an adjustment period, and everything will click.”

Mike Napoli’s decision to test his strained right hamstring before it was ready last week in Toronto will cost the catcher at least another week on the DL, maybe more.

“I was going at a good pace and probably pushed it too hard,” he said. “I was running at 75% and felt good, I tried to pick it up and I wasn’t ready.”

Scioscia said he thought Napoli would resume running by the end of the week.

Bartolo Colon, on the DL because of an elbow irritation, will throw the first of at least two simulated games today. Barring a setback, the right-hander will probably begin a rehab assignment early next week.

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mike.digiovanna@latimes.com