John Lackey expected to open season on disabled list

Angels ace John Lackey is expected to open the season on the disabled list after an MRI test revealed inflammation in his throwing elbow, a setback that casts further doubt on a rotation already racked by injury.

Manager Mike Scioscia said Friday that “right now, it’s definitely unlikely” Lackey will be ready to pitch the April 6 season opener against Oakland.

Ervin Santana, an All-Star in 2008, is expected to miss most of April because of a sprained elbow ligament. Though Kelvim Escobar is well ahead of schedule in his recovery from shoulder surgery, the right-hander won’t return until late April at the earliest.

That means the Angels, who were expected to have one of the strongest starting staffs in baseball, will probably open the season with a rotation of Joe Saunders, Jered Weaver, Dustin Moseley, Nick Adenhart and Shane Loux, who was rocked for seven runs and 10 hits in four innings of Friday’s 9-3 exhibition loss to Arizona.

“We have starting pitching depth, but right now we’re stretching it as far as we’re comfortable with,” Scioscia said. “But we’re very comfortable with the way Adenhart is throwing, the way Loux has been throwing, and Moseley is reaching his projected talent level -- he’s throwing the ball as well as he has in his life.

“Obviously, any rotation without Lackey, Santana and Escobar is not going to be as strong, but we have confidence these guys are going to give us a chance to win.”

Lackey, who sat out the first six weeks of last season because of triceps tendinitis, the first trip to the DL in his career, began to feel tightness in his forearm near the inside of his elbow during last Sunday’s start against Kansas City. The right-hander tried to play catch Thursday, but when he continued to feel discomfort he was sent for the MRI exam, which showed inflammation but, according to Scioscia, no structural damage.

The team is expected to have a better handle on the injury after Dr. Lewis Yocum, team physician, reads Lackey’s MRI exam results today. Until then, Lackey said, “we’re shutting it down for a couple of days.”

The Angels could pursue a quick rotation fix by signing a veteran free agent such as Pedro Martinez or Paul Byrd. If Lackey or Santana are out for extended periods, the Angels could rekindle trade talks for San Diego Padres ace Jake Peavy.

Crouching Angel

Mike Napoli, relegated to designated hitter while he rehabilitated his surgically repaired throwing shoulder, made his first spring appearance behind the plate Friday, catching five innings and throwing out the only runner who tried to steal.

Napoli, who hit 20 homers in 78 games last season, made a strong, accurate throw to second to get Arizona’s Conor Jackson.

“It was a little weird back there, because I haven’t caught and thrown in a game since the last game of last year,” Napoli said. “But it felt good. My arm is in shape, and we did it the right way.”

Short hops

Loux’s spring earned-run average jumped from 0.84 to 4.91 after he gave up three runs in the second inning and four in the fourth. . . . Escobar is scheduled to throw 45 pitches today in a minor league game, his second start since shoulder surgery. His fastball hit 96 mph in his first start Monday. . . . Moseley will also pitch in a camp game today, with a target of 100 pitches.

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mike.digiovanna@latimes.com