Scribner will replace JC Ramirez, who felt pain in his right elbow after his start Saturday at Baltimore. Ramirez, who could miss the rest of the season, leads the Angels in wins (11) and innings pitched.
Ramirez's innings total -- 147 1/3 -- is more than he had pitched in his entire major league career (126 1/3) going into this season. Ramirez, who broke into the majors in 2013, had been a reliever until this season.
"You never know where a guy is and if there's an endpoint somewhere," Angels manager Mike Scioscia said. "He had rebounded from every start very well and really had no issues along these lines.
"We monitored him very closely. He's been doing his routine, doing his work. His bullpens have been good. So it's hard to say exactly what the cause is. Right now we're just going to have to deal with it."
The team will deal with it by turning to Scribner, who was up with the big club earlier this season and pitched well.
Scribner, 26, is a 6-foot-3, 190-pound right-hander who had pitched in the minors since he signed as an undrafted free agent with the Houston Astros in 2013. He was called up for the first time late last month and made two relief appearances before getting his first start on Aug. 4 against the Oakland A's.
His best performance came in his second start, Aug. 9 against Baltimore, when he gave up one run and two hits in five innings to get the win. Overall, he is 2-0 with a 3.46 ERA for Los Angeles. In 20 games (19 starts) for Salt Lake, he is 11-4 with a 4.35 ERA.
Scribner is matched up against the Rangers' Martin Perez, who is 8-10 with a bloated 5.26 ERA in a team-leading 24 starts. Perez, though, may have figured some things out.
After he was tagged for seven runs in a loss to the Minnesota Twins on Aug. 4, Perez had lost four straight starts and was 5-10 overall. But he came to the conclusion that we was tipping his pitches.
After watching video of himself, Perez said his hand was positioned differently when he threw a fastball compared to when he threw an off-speed pitch.
"It's a big difference," Perez told the Fort Worth Star-Telegram. "They're supposed to be the same spot every time. I think it's been happening a lot."
Rangers pitching coach Doug Brocail wasn't necessarily buying it.
"I don't want anybody making excuses," Brocail told the Star-Telegram. "I don't want that to be a cop-out that makes us not work hard in our next side session."
Whether or not it was an issue, Perez has turned things around since his discovery, going 3-0 with a 4.05 ERA in three starts.
Perez is 2-4 with a 3.53 ERA in 10 career games (nine starts) against the Angels. He took a loss on April 30 (four runs, 5 2/3 innings) in his only start against Los Angeles this year.
The Rangers would take three of four from the Angels if they get the win Thursday. Texas earned a 7-5, 10-inning victory Wednesday, getting two homers from Adrian Beltre.