IRVING, Texas - The Cowboys fear running back DeMarco Murray suffered ligament damage in his foot but not a season-ending Lisfranc injury, according to sources.

The X-rays taken at Baltimore from Sunday's 31-29 loss to the Ravens were negative, but Murray is undergoing an MRI Monday morning and the results are not yet known.

Murray, who had his rookie season cut short last year because of a fractured ankle against the New York Giants, sprained his foot in the first half Sunday in which he picked up 90 yards. He had one third-quarter carry for 3 yards but was kept out of the rest of the game.

After the game, Murray said he wanted to return, and he was not in a walking boot.

If Murray misses an extended amount of time, the Cowboys would turn to Felix Jones. He picked up 92 yards on 18 carries against Baltimore but missed time in the second half to get intravenous fluids because he was cramping.

Without Murray and Jones, Phillip Tanner and Lance Dunbar took over the running back duties and combined for 42 yards on 10 carries.

It is possible the Cowboys could look for more veteran running back help if Murray is out. Last year they signed Sammy Morris with four games to play after Murray hurt his ankle and Tanner was on injured reserve because of a hamstring injury.

This could be Jones' last best chance to show he can be an every-down running back as he hits free agency after this season.

He failed the conditioning test to open training camp and had a woeful preseason that carried over into the regular season. Prior to Sunday's game he had 13 yards on three carries in the first four games.