Updated

The Atlanta Falcons have lost cornerback Brent Grimes to a season-ending Achilles tendon injury.

Grimes went out in the fourth quarter of Atlanta's 40-24 win at Kansas City in the season opener. Coach Mike Smith announced Monday the cornerback will need surgery, costing Atlanta one of its best defensive backs.

Grimes was a Pro Bowler in the 2010 season and got the franchise tag this past offseason when he couldn't agree on a new contract, receiving a salary of $10.2 million. The Falcons traded for Asante Samuel, looking to have a trio of top coverage cornerbacks in the pass-happy NFC West. Samuel, Grimes and Dunta Robinson started against the Chiefs and were on the field together for all but 11 plays.

But the new arrangement lasted only one game.