CHICAGO -- Welington Castillo has a partial meniscus tear in his right knee and will need arthroscopic surgery, meaning the Cubs catcher won't return for the remainder of this season.
Castillo, who had an MRI on Friday, exited Thursday's 5-1 victory over the Brewers in the sixth inning after running out a ground ball.
"With proper rehab, it's the type of thing you come back 100 percent from with rehab," Cubs president of baseball operations Theo Epstein said.
A conservative estimate for the rehab timetable is four to six weeks following surgery. A date for Castillo's surgery was not announced.
"He had a fantastic year," Epstein said. "I think it's a developmental success story in every facet. With catching, it starts with winning the trust with your pitchers and putting the right fingers down, and he did an outstanding job. He's really involved in game planning and game calling. I think every pitcher now loves throwing to him. He did an outstanding job defensively. His blocking has been at an elite level."
Epstein added that despite a slow start to the season offensively, Castillo -- who was hitting .271 with 23 doubles, eight home runs and 32 RBIs in 380 at-bats -- made the necessary adjustments and finished strong.
"He made some adjustments and learned a lot about his swing and has gotten pitches that he can drive and is doing damage with them," Epstein said. "He's always been a super-talented player and great kid, and this is one of those years he's established himself. Unfortunately, it ends this way, but he had a full year."
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. Manny Randhawa is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.