Ryu said he experienced the same discomfort in the middle of his shoulder blade while pitching in Korea in 2011, and he was “back on track” in 10 days. He said it already feels better than it did earlier in the week.
The injury forced him to sit out for 19 days, not 10. Maybe he meant 10 in addition to his normal rest? This isn’t a big deal, since Ryu will be on DL for 15 days either way. The bigger issue is that it doesn’t look like Ryu returned at full strength. He returned in the bullpen. Between the injury on June 28th and his start on September 8th, Ryu only pitched 3-2/3 relief innings. He did not pitch at all between August 2nd and September 2nd after allowing three runs and getting one out.