Nick Swisher is heartbroken Christian Yelich won't return to the diamond this season after hurting his knee ... and he tells TMZ Sports he thinks the Brewers might be done after the devastating injury.
"I don't know, man," Swisher says. "That's a big hurdle to get over at this point in time."
Yelich -- arguably the frontrunner for the National League's MVP award -- fouled a ball off his right knee Tuesday night ... and, after the game, the Brewers said he'd be done for the season with a broken knee cap.