Krook was optioned to Triple-A Scranton/Wilkes-Barre by the Yankees on Tuesday, Bryan Hoch of MLB.com reports.
Krook was sent down to make room for Jhony Brito with Brito coming up from Triple-A on Wednesday to start against the Mariners. Krook made just one appearance while up with the Yankees, and he allowed five runs in 1.2 innings in that game against the Red Sox on Friday.