"It's a tough break for us," manager Tony La Russa said Tuesday. "Tougher for him."
Grandal, 32, fell to the ground moments after taking a pitch from Twins reliever Caleb Thielbar. At first, it looked like Grandal injured his ankle or calf, but further examination revealed a torn tendon in the knee.
"It was a twist as he made his swing," La Russa said. "Something got caught."
Grandal is hitting .188 with 14 home runs, 38 RBIs, 60 walks and a .388 on-base percentage in 63 games this season. The White Sox have the third-lowest ERA in the American League with Grandal as their starting catcher.
Despite his low batting average, Grandal has hit some key home runs while the White Sox have maintained first place in the AL Central.
"He had a lot of big hits for us," La Russa said. "Someone else has to get them now."
To replace him on the roster, the White Sox called up 27-year-old catcher Seby Zavala from Triple-A Charlotte. He has played in five major league games in his career, all for the White Sox in 2019.
The injury adds to a long list of White Sox players on the mend, including left fielder Eloy Jimenez (pectoral), center fielder Luis Robert (flexor tendon) and second baseman Nick Madrigal (hamstring). All but Madrigal are expected back this season.
"It's only as difficult as you allow it to be," La Russa said. "If we want to act frustrated and discouraged that we've been unlucky then we'll lose an edge."