Surgery setback for Wigan Athletic star
The loss of the 33-year-old for the festive period and beyond is the latest blow to hit boss Paul Cook, who saw his side concede a stoppage-time winning goal at Stoke on Saturday to leave them one point clear of the Championship drop zone.
And Cook says his inability to call on Fox or Cedric Kipre - who was suspended after his red card against Brentford - was a telling factor at the bet365 Stadium.
"Absolutely," he said. "Without a shadow of a doubt.
"Can Chey Dunkley and Charlie Mulgrew play any better than that? They can't.
"We did not have another centre-half on the bench. That's the brutal reality of life in this division.
"As a manager, the biggest pain you have is when you can't help your team.
"I couldn't help my team today, and that's the saddest thing of all.
"We're without Danny Fox through injury and Cedric Kipre through suspension.
"When Stoke bring on (Mame) Diouf and (Sam) Vokes, you'd be looking to put on a third centre-half.
"But we just didn't have one!
"And I don't know how I can help them except shutting my eyes and praying."
Cook then revealed the extent of the problem with Fox.
"Danny's out for seven weeks," the Latics boss added. "He's had an operation on his groin."