GLENDALE, Ariz. -- Starting pitcher Hyun-Jin Ryu was held out of workouts with the Los Angeles Dodgers for the second straight day Thursday because of stiffness in the middle of his back.

Ryu said he doesn't anticipate this setback delaying the start of his season.

"I'm not worried at all," he said Thursday.

An MRI taken Wednesday showed no structural damage, manager Don Mattingly said. He said he is hopeful Ryu won't miss enough time in camp to delay the start of his season.

"I've had enough back stuff to know it can feel bad today, you wake up tomorrow and, all of a sudden, you're back," Mattingly said.

"At this point, I don't think any of us are worried about the timetable. If it were to linger and go on and on, then obviously it would start to mess with his schedule."

Ryu, who is 28-15 with a 3.17 ERA in two major league seasons, is being counted on as the Dodgers' No. 3 starter behind Clayton Kershaw and Zack Greinke. He threw a bullpen session Tuesday, but he reported discomfort afterward. On Wednesday, he told Korean reporters that he thought he would resume workouts the following day.

The Dodgers have had reason to be worried about the health of their rotation this spring. Greinke had a precautionary injection of lubricant into his elbow last week and has resumed throwing off a mound. No. 5 starter Brett Anderson is coming off back surgery and is getting extra rest between bullpen sessions.