CLEVELAND -- Browns Pro Bowl center Alex Mack broke his left leg during Sunday's 31-10 win over the Pittsburgh Steelers.
Mack, who had never missed a snap during his pro career, was hurt while blocking on a running play in the second quarter. He was face down in the grass for several minutes before a cart was brought out to drive him to the locker room.
Browns coach Mike Pettine said the initial diagnosis was a broken leg. The team will have more details on Mack's injury Monday.
As he was being treated by Cleveland's medical staff, several Steelers approached Mack to wish him well. All of Mack's teammates came out onto the field to support him, and he acknowledged the cheering crowd as he was taken away.
Right guard John Greco slid over to replace Mack and Paul McQuistan filled in at right guard. Greco had never played center in a game in his career -- going all the way back to high school.
A former first-round draft pick, Mack had played 5,189 consecutive snaps coming into the game. He signed a five-year, $42 million contract in March.
Quarterback Brian Hoyer said it was hard to see Mack taken off the field.
"It's tough," Hoyer said. "Alex, other than Joe Thomas, has been the anchor of that line long before I got here. I know how much it means to him and when you see the whole team come over and check on him, it shows how much he means to this offense."
In the first quarter, Browns defensive end Armonty Bryant was carted off with a sprained knee. Pettine did not have a detailed update but said the "news isn't good on Armonty."
Bryant started in place of Phil Taylor, who underwent knee surgery last week and could be out for several more weeks.
The Steelers had a rash of injuries.
Starting nose tackle Steve McLendon sprained his right shoulder. Free safety Mike Mitchell sprained his left knee and defensive end Brett Keisel also sprained his left knee.
Coach Mike Tomlin said the injured players will be treated and evaluated.
Browns rookie cornerback K'Waun Williams sustained a concussion in the third quarter on a pass play. Williams appeared to get hit by a teammate while defending a pass downfield. He walked off the field under his own power and immediately went to the locker room for further tests.
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