File, Associated Press
FILE - This is a 2011 file photo showing Kansaqs City chiefs football player Brandon Siler. The agent for Siler says the Kansas City Chiefs linebacker tore his Achilles tendon during practice and will miss the entire season. David Canter confirmed the injury in a text message to The Associated Press on Wednesday, Aug. 24, 2011.

KANSAS CITY, Mo. — Kansas City Chiefs linebacker Brandon Siler tore an Achilles tendon during practice this week and is the latest to join a growing list of NFL players to sustain the season-ending injury.

Siler's agent, David Canter, confirmed the injury in a text message to The Associated Press on Wednesday. He did not know which Achilles was hurt, but said Siler already had surgery to repair it.

"We're both beside ourselves upset," Canter said.

Siler was competing for the middle linebacker spot alongside Derrick Johnson after signing with the Chiefs as a free agent. Siler had looked good throughout fall camp after picking up 44 tackles, one sack and one interception in 12 games with the San Diego Chargers last season.

The Chiefs' policy is to not discuss injuries, although they're quickly stacking up.

First-round draft pick Jonathan Baldwin hurt his right thumb in a reported locker room altercation with running back Thomas Jones, and fellow wide receiver Steve Breaston also has missed some practice time. Offensive linemen Jared Gaither, Ryan O'Callaghan and Darryl Harris have been out at various times, along with cornerback Brandon Flowers and linebackers Gabe Miller and Eric Bakhtiari.

The Chiefs should be able to withstand the loss of Siler, who could also have contributed to special teams. Jovan Belcher has made 131 tackles while playing significant snaps the past two seasons, and Demorrio Williams and Cory Greenwood provide additional depth.

Siler's injury is the first significant one for the Chiefs, though hardly the first round the league, where some believe the NFL lockout has contributed to more season-ending injuries.

Detroit's second-round draft pick, running back Mikel Leshoure, tore an Achilles tendon earlier in fall camp. Browns punter Reggie Hodges sustained the same injury after he took a snap in the end zone, took one step and dropped like a sack of flour. Philadelphia defensive end Victor Abiamiri and Bengals linebacker Roddrick Muckelroy are among the other players to tear their Achilles.

The lockout wiped out organized team activities and the ability for players to use team facilities during the summer months, which some argue resulted in players arriving at camp out of shape.

Browns linebacker Scott Fujita, a member of the players' executive committee, has said he is personally monitoring some of the reported injuries from other training camps. He's also asked trainers to keep him updated on missed practices to determine whether the lockout had any effect.