Regardless, he's almost certainly done for this season.
"Anytime a guy says his elbow hurts, it's kind of scary," said manager Don Mattingly.
The 22-year-old De La Rosa struggled in a loss to the D-backs on Sunday, making 103 pitches in four innings while allowing five runs and walking four. Included were back-to-back home runs by Ryan Roberts and Gerardo Parra.
"He looked different," said Mattingly. "His body language. He wasn't working quick like usual. His tempo was off. We were seeing something different. It must have been that."
De La Rosa told the media after the game that he felt fine physically, but actually had already told trainer Stan Conte that his elbow tightened after a third-inning pitch.
It was hard to tell by his velocity. He hit 99 mph five times Sunday and his last pitch was clocked at 97. Conte said there was no swelling.
"His last 'pen was really good, but then I heard he felt it in his last 'pen," said Mattingly. "Obviously, he didn't tell anybody. We wouldn't take any chances. But as a player, you're always feeling something and you figure it will probably go away."
Mattingly said Ely would initially report to the bullpen and, with a day off Thursday, the club was considering skipping De La Rosa's spot one time before inserting a fifth-starter substitute.
"I thought I saw something with his mechanics around the third inning," said catcher Dioner Navarro. "After the game, I talked to him and he said he had something with his arm. I guess he was trying to find a way to throw that didn't hurt."
De La Rosa is 4-5 with a 3.71 ERA since his May callup from Double-A Chattanooga. He had allowed only four home runs in his previous 56 innings.
At Albuquerque, Ely was 6-4 with a 5.43 ERA. He pitched in two games for the Dodgers during an early season callup with one start, going 0-1 with a 6.23 ERA. He was 4-10 last year with a 5.49 ERA.