The long snapper was participating in his 215th career game, but he went down in the second quarter of the team's 31-20 win over the San Diego Chargers. The team put him on season-ending injured reserve on Monday.
"It's tough, Pat is the symbol of consistency as far as his play goes," Bears linebacker Nick Roach said Monday. "He has a great game, every game, and hardly ever gets any recognition for it. He's a big part of the team and our special teams captain. He's taken for granted, but I think he embraced that, because nobody ever had to wonder what he was doing or if he could get it done. He's a great guy to play with and I'm sure he'll mentor whoever has to step in from here on out."
The Bears also released defensive end Mario Addison on Monday, leaving the active roster at 51 players. The Bears will likely sign another long snapper and also a veteran quarterback since Jay Cutler is out.
Mannelly immediately limped toward the Bears' sideline, and athletic trainers began examining him. After several minutes of being looked at by athletic trainers, Mannelly walked to the locker room under his own power.
Since joining in the Bears as a sixth-round pick in 1998, Mannelly has played the most games in franchise history. Mannelly has undertaken long-snapping duties in all but three games of his career, handling 2,017 of 2,037 Bears snaps since 1998 coming into Sunday's game.
Mannelly was playing in his team-high 147th consecutive game.
Information from ESPNChicago.com's Michael C. Wright and Jeff Dickerson was used in this report.