Zunino will undergo surgery next week and the expected recovery time is six weeks.
"It's something that I'm going to have to deal with and come back through a speedy recovery," Zunino said. "Yeah, it's frustrating, but it's just another thing you deal with as a player."
To help replace Zunino, Seattle signed free agent catcher Humberto Quintero, who was designated for assignment by the Phillies on Wednesday. Quintero hit .250 with two home runs and nine RBIs in 24 games with Philadelphia.
Zunino was injured in the second inning of Thursday night's game when he hit an RBI single. He remained in the game for three more innings before being removed and an MRI on Friday morning confirmed the injury. Depending on how Zunino's recovery goes, there is a chance he could miss the rest of the season.
"It's unfortunate for Mike and for us," Mariners acting manager Robby Thompson said. "It's one of those freak things."
Zunino's play behind the plate has been part of the Mariners' resurgence in July. He was called up June 12, soon after Jesus Montero was demoted, and has played in 29 games, hitting .242 with two homers and 10 RBIs.
The Mariners have used six different catchers this season. With Zunino out, Quintero will split time with 41-year-old Henry Blanco, whom the Mariners signed in June after he was released by the Blue Jays. Blanco has played 26 games this season between the two teams and is hitting .171 with a home run and seven RBIs. Since Blanco has had more time with the Mariners' pitching staff, Thompson indicated he would shoulder most of the catching duties for now.
"We're going to lean on him quite a bit here on out," Thompson said.