Ryu is eligible to return from the disabled list on Tuesday, but he will at least need to throw a bullpen session, if not a simulated game or rehab start, before he rejoins the Dodgers' rotation.
"He's pain free, and that's the best thing," said Mattingly. "There's no indication it's something serious. When he's able to throw a 'pen, he'll get right back on it."
Ryu played catch with Dan Haren, who is scheduled to start Monday. Haren has been dealing with back stiffness and did not participate in pitchers' fielding drills Friday, but Mattingly said Haren is "fine."
Mattingly also indicated that A.J. Ellis continued to work at the club's Arizona facility, catching seven innings Friday, getting a hit and getting hit by two pitches. Ellis will serve as designated hitter on Saturday and Mattingly said a Minor League rehab assignment could be next.
Ken Gurnick is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.