Backup John Baker was given the starting nod, because Castillo was still on his way to the ballpark from Triple-A Iowa when the lineup was posted, but Castillo was available off the bench.
Castillo was placed on the DL on June 3 with a strained left rib cage. He should help restore some offensive production to the catching spot, as Whiteside and Baker averaged a .147/.183/.168 line in Castillo's absence. Of the 18 games Castillo missed, Baker started 11 and Whiteside seven. Castillo was hitting .242/.287/.385 in 43 games entering Sunday's action.
"More than anything, just having him back, you know, he's been with the club here now developing as a catcher and being a part of the Cubs moving forward," manager Rick Renteria said. "Just having him back and healthy, being able to get out there with his teammates will be good to have."
Whiteside could return to Triple-A Iowa if he clears waivers. Renteria hopes that's the case.
"He's done a nice job for us," Renteria said. "He's an excellent receiver -- a nice game for us [Saturday]. He helped the transition while Weli went down and continued to have the ball moving forward, and from a very selfish perspective, I think we as an organization hope he clears."
Joe Popely is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.