I wouldn't say Koby has been solid. I don't think a 6.14 ERA, 1.23 WHIP, 6 Ks, 2 saves in 7.1 innings is solid. Average? Adequate? Maybe.
Like was mentioned, he's approaching his innings limit so he'll be used sparingly anyway.
The Indians are in a mode to figure out what will help them win next season. Koby at closer is not in that formula. I think they'll give Perez one more shot this season.
Perez in the last month has posted a 2.53 ERA, 0.66 WHIP, 1 save, 7 Ks, in 10.2 innings.