Zack Martin, arguably the best guard in football, suffered a knee injury Saturday night and won't return to the Cowboys' preseason game vs. Cincinnati.

Martin, who in June signed a six-year, $84 million extension including $40 million guaranteed that made him the NFL's highest-paid guard, appeared to suffer the injury on a low hit by Bengals CB Dre Kirkpatrick. After spending about 10 minutes in the medical tent and emerging with his right ankle heavily taped, according to Cowboys sideline reporter Kristi Scales, Martin was taken to the locker room and ruled out for the remainder of the night.

Jerry Jones provided an encouraging update on Martin after the game: "I just want to say we've got more to gain from [MRI on Sunday]," Jones told reporters, via Pro Football Talk's Charean Williams, "but from what we've seen, I'll sleep good tonight on Martin."

Dallas' O-line was largely considered the NFL's best unit for several seasons entering 2017, when Tyron Smith's health and the free-agent departure of Ronald Leary, contributed to an uncharacteristically down year.

Now, the health of Martin, who has gone to four consecutive Pro Bowls since the Cowboys selected him 16th overall out of Notre Dame in 2014, gives the Cowboys another concern along the interior, where C Travis Frederick has been slowed by stingers in recent days and second-round Texas product Connor Williams is being plugged in at left guard.

If Martin were to miss time, the Cowboys could consider 27-year-old Joe Looney (13 career starts) or perhaps swing tackle Chaz Green as contingency plans. But after the retirement of Jason Witten and release of Dez Bryant signaled a sea change to the passing attack, the Cowboys intend on riding their offensive line and bellcow Ezekiel Elliott more than ever. That plan largely depends on a healthy Martin and Frederick anchoring the offense up front.