The San Francisco 49ers fear wide receiver Michael Crabtree tore his Achilles tendon on Tuesday, league sources told ESPN NFL Insider Adam Schefter.
Crabtree is undergoing additional tests to confirm the injury, the sources said.
USA Today Sports, citing a person informed of the injury, is reporting that Crabree tore his Achilles.
While a torn Achilles usually was considered a season-ending injury, both Baltimore Ravens linebacker Terrell Suggs and Tampa Bay Buccaneers defensive end Da'Quan Bowers were able to return to play during last season after suffering the injury earlier in the year.
Crabtree, 25, had his best season in 2012 for the NFC West champion 49ers, with 85 receptions for 1,105 yards and nine touchdowns.