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 Wednesday. He didn’t 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.

“I don’t really know what happened,” said Demorrio Williams, who has been competing with Siler for playing time. “I just saw him land on the ground.”

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. Fellow wide receiver Steve Breaston also has missed some practice time, along with offensive linemen Jared Gaither, Ryan O’Callaghan and Darryl Harris, 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 Williams and Cory Greenwood are in the mix.

“I think we have good depth,” Johnson said. “It’s always tough to lose a linebacker, and it’s hard. It’s hard. But this is a violent sport.”

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.

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.