The Dallas CowboysThe tough season just got tougher on Monday.

Dak Prescott is expected to miss “several weeks” with a hamstring injury that is “more serious than expected,” sources said. Tom Pelissero and Ian Rapoport of the NFL Network. It’s unclear if the Cowboys will place Prescott on injured reserve.

defender suffered the injury in the second half of Dallas’ loss to the Atlanta Falcons in Week 9 when an offensive lineman appeared to roll into Prescott’s left leg on a play late in the third quarter.

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Prescott told reporters after the game that he “felt something pulling” and “felt something I’ve never felt.” He underwent an MRI, but the extent of the injury is unknown, but will get a second opinion.

The Cowboys turned to eight-year veteran Cooper Rush, who went 13 of 25 for 115 yards with a touchdown.

It’s been a difficult season for the Cowboys, who fell to 3-5 after Sunday’s loss, and it’s only gotten more difficult with the news that Prescott has been ruled out indefinitely. Rush figures to be the starter in his teammate’s absence, but with the NFL trade deadline on Tuesday, it will be interesting to see if the Cowboys trade another quarterback.