Darrius Heyward-Bey sits out

ANDERSON, Ind. -- Indianapolis Colts receiver Darrius Heyward-Bey sat out of the team's morning walk-through and afternoon practice in pads Monday because of what the team is calling a sprained left knee.

A team spokesman described the injury, which happened in practice Sunday, as not serious.

Heyward-Bey stood on the field for both practices while wearing a brace on his knee Monday.

He's spent the first part of training camp lining up opposite of Reggie Wayne at receiver.

Teammates and coaches insisted after Monday's morning workout that the receiver might be back on the field soon.

"Yeah, it stinks when a guy goes down but it is the nature of football and hopefully it is not too serious, I don't think it is," quarterback Andrew Luck said. "I feel very comfortable with all those guys, they do the right things, they run the right routes at the right time, they know how to get to the spot."

Depth at receiver will become a concern for the Colts if Heyward-Bey, who signed with them in the offseason after spending his first four years with the Oakland Raiders, is out for an extended period of time.

T.Y. Hilton will likely step in to the No. 2 receiver spot, but the remaining seven receivers in camp have combined for 12 catches in their career.

"We feel like our backups are very capable," offensive coordinator Pep Hamilton said earlier in the day Monday. "I expect the next guy to step up."

Heyward-Bey isn't the only concern.

Linebacker Jerrell Freeman, who set the Colts' single-season record for tackles (203), sat out with a shoulder injury. The team did not provide details of the injury or how much time Freeman might miss.

Colts cornerback Greg Toler did make it back to practice after missing three full days with a concussion.

Also Monday, the Colts signed free agent fullback Robert Hughes. The 5-foot-11, 235-pound Hughes played in five games with the Colts last season.

Mike Wells covers the Indianapolis Colts for ESPN.com. Information from The Associated Press was used in this report.