Ryu, who has missed the last season and a half with shoulder surgery, could return as early as Thursday, and if not then, soon after next week's All-Star break.
Kershaw's herniated disk necessitated the Norris trade, as well as an epidural pain-killing injection. Educated guesses range from four to eight weeks on the sidelines for a disk that doesn't need surgery, and he's already been down for one week. Teammate Scott Van Slyke was out for two months with a similar injury.
"Everything that's happened in the three or four days since the epidural has been extremely positive," said Friedman. "That being said, I think we'll know more probably in the next week. You need to give it time past the epidural to get a sense of improvement, then we'll go from there.
"So much of it is specific to the individual. Talking to Dr. [Robert] Watkins, it just really varies guy to guy. There's a five-step program that Dr. Watkins has that Kersh is starting. At some point in that is when you can start throwing. Obviously, that would be a big first step as soon as we can get there in a responsible way, we'll do it."
As the pain subsides from the injection, Kershaw will do core exercises to strengthen muscles hoping to prevent another nerve episode. That leads to resumption of throwing, the build-up of arm strength and rehab games before a return to the Major League rotation.
Norris' welcome debut, the rebound to form of Scott Kazmir on Saturday night and the consistency of Kenta Maeda provide the current top three of the rotation, followed by McCarthy. Julio Urias, as well as he has pitched, is still 19 and figures to be shut down, or at least throttled back for later use. Ryu's return could hasten Urias' break.
Alex Wood (elbow) is throwing off a mound and could be back by the end of the month. Brett Anderson (back surgery) is hopeful for an August return, although the club thinks September is more realistic. At Triple-A, Ross Stripling, Jose De Leon, Brock Stewart (optioned Sunday for McCarthy's return) and Carlos Frias are on call if injuries create another crisis.