Wigan boss Paul Jewell felt injuries to Arjan De Zeeuw and Matt Jackson hit his side hard at Newcastle.
The Magpies came back from a goal down to claim a 3-1 win, but Wigan were leading when Jackson and De Zeeuw were forced off.
Jackson has damaged knee ligaments and De Zeeuw has a suspected fractured collarbone and Jewell felt his side never recovered from the dual loss on Tyneside.
"It was difficult," Jewell told Sky Sports News. "When you lose your two centre backs within a minute of each other you know you are going to be up against it.
"De Zeeuw has broken his collarbone, we think. Matt Jackson has done his knee ligaments, we don't know the extent of that and McCulloch was not feeling well.
"They are three big players for us and we missed them."
Jewell felt his side were the match of Newcastle until the injuries.
"We started brightly, scored a wonderful free kick," he declared. "Their first goal the referee did not give the penalty, it was the linesman, so I don't know. The second one was a free header from a corner, which was disappointing.
"It was always going to be an uphill struggle. We stuck at it and didn't disgrace ourselves, but we had a scratch team out there and found it difficult."
Alan Shearer netted twice for Newcastle and Jewell paid tribute to the Geordie legend.
"Shearer did what he does best," added Jewell. "He was too much for our centre halves today. His legs are not what they used to be but he was too much as he knows the game.
"He is a top-class player and showed us how to play centre forward. He might not have the legs, but he has the know-how, the brains and the technique."
Jewell feels his side have performed with credit this season.
"We have not had a great last six or seven weeks, but we have earned the right to be in this division next season and I can't speak highly enough of my players.
"We can look back and say we have made great strides, but next season we have to do even better. It will be tough for us next season. We have to be better in all areas."