Cowboys guard Zack Martin and safety Xavier Woods suffered separate injuries during Saturday night's 21-13 preseason loss to the Bengals. Neither player returned to the game.
Martin limped off the field in the second quarter while trying to block Bengals cornerback Dre Kirkpatrick, who hit Martin low on a running play to the right side.
Cowboys head coach Jason Garrett said that doctors were "somewhat optimistic" after Martin's evaluation. Martin just signed a 6-year, $84 million extension in June.
"He hurt his knee and we'll get an MRI on it tomorrow," said Garrett. "The initial evaluation was positive."
Safety Xavier Woods will also be evaluated Sunday after straining his hamstring on a diving interception attempt in the second quarter.
Center Travis Frederick did not suit up for the game while he deals with shoulder stingers. Joe Looney started in Frederick's place.
Running back Bo Scarbrough (hip) and defensive end Datone Jones (knee) were among the other Dallas players banged up in the loss.