For a brief moment, it looked as though the Detroit Lions might get a major boost for their playoff push when veteran center Frank Ragnow decided to step out of retirement. That optimism didn’t last long.

Ragnow’s attempt to rejoin the team came to an abrupt end on Friday when he did not pass his physical, with doctors diagnosing him with a significant hamstring injury.

The setback couldn’t come at a worse time. If Detroit falls to the Dallas Cowboys on Thursday night, head coach Dan Campbell may find his team slipping further out of postseason contention—while former Lions offensive coordinator Ben Johnson could guide the rejuvenated Chicago Bears into the playoffs.

“Frank Ragnow came in yesterday and completed the standard return-to-team process,” the Lions announced in a statement on social media. “During his evaluation with our medical staff, he did not pass his physical.

“The examination showed he has a Grade 3 hamstring tear, which makes him unavailable for the remainder of the regular season. Because of that, Frank will not be rejoining the roster. He has always embodied toughness and selflessness. He will always be part of the Lions family.”