SANTA CLARA, Calif. -- Arizona Cardinals running back James Conner suffered a season-ending right ankle injury during Sunday's loss to the San Francisco 49ers , a source told ESPN's Adam Schefter.

Conner was carted off the field after a 9-yard run with 12:26 remaining in the third quarter of the Niners' 16-15 victory . The injury is considered "severe" and will require surgery, the source told ESPN on Sunday night.

After the game, Arizona coach Jonathan Gannon said he didn't know the severity of the injury, as a prognosis hadn't yet been made.

The Cardinals are heading into a short week before hosting the Seattle Seahawks on Thursday night.

Players from both teams took a knee as athletic trainers quickly attended to Conner after he went down. The entire Cardinals bench walked

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