Coach Pat Shurmur said Mack came to the team's facility on Monday showing appendicitis symptoms. Mack had "soreness and the tenderness that would point to that," Shurmur said.
Haden's injury could be more severe. He was seen wearing a knee brace around the Browns' headquarters, and Shurmur said Haden will not practice Tuesday.
Haden has been credited with eight pass breakups this season, and losing him for any length of time would be a devastating blow to the Browns.
Mack had his operation on Monday and Shurmur doesn't know how long the 25-year-old, who made the Pro Bowl last year in his second NFL season, will be sidelined.
The 6-foot-4, 310-pound Mack hasn't missed a single play since the Browns drafted him in the first round in 2009, starting 36 consecutive games.
"He's tough as nails because he was feeling a little queasy," said right tackle Tony Pashos, who watched a game on TV with Mack on Sunday night. "He was talking about some issues then, too, and I was like maybe it's just something you ate."
The Browns (2-2) have a bye this week, which will give Mack more time to heal. As far as Pashos is concerned, Mack doesn't need any rest.
Copyright 2011 by The Associated Press