Instead of just dealing, Jepsen has been "working on some things out there."
That, he added, has to stop -- immediately.
"I'm getting tired of it," he said, having surrendered three hits and a run while getting one out on Friday night in the ninth inning against the Athletics. "This isn't me.
"I'm not the type of pitcher who can work on stuff and be successful. I've got to go out there and be 100 percent. I'm giving up a single, a broken-bat hit, as opposed to going after them and putting them away."
What's strange about it, Jepsen added, is that he feels so strong physically after taking five days off starting on Sept. 20.
"My velocity is fine, I'm throwing strikes, my slider's good, my breaking ball's good," he said. "I'm just lacking a go-after-'em mentality. I've got to get that back, absolutely."
He'll get his chance in the season finale on Sunday, manager Mike Scioscia said.
"Jep's fine," Scioscia said. "His stuff is good."
Since the arrival of July, Jepsen has made 39 appearances, yielding 12 earned runs in 41 2/3 innings (2.59 ERA) with 14 walks and 41 strikeouts.
Scioscia said he's not concerned about a few nicked-up middle infielders with the American League Division Series against Boston looming, given that they'll have plenty of time to rest and recuperate early next week.
Izturis dinged his left knee in a collision with Rangers first baseman Andruw Jones on Wednesday, the same night shortstop Erick Aybar bruised his right hand bunting. Howard Kendrick developed a staph infection in his right knee sliding into home on Sept. 26.
Kendrick and Aybar were in the lineup on Saturday, and Scioscia hopes to get Izturis a few at-bats on Sunday, adding, "Izzy will be fine for the playoffs."
Izturis was recovering from a torn thumb ligament last October and was unavailable for the ALDS, which was won by Boston in four games.