Ricketts went to ground in the second half at the DW Stadium while tracking Latics substitute Victor Moses and had to be carried off on a stretcher.
"He has damaged his Achilles and it doesn't look great at this time," said Coyle, whose team ran out 1-0 winners thanks to Ivan Klasnic's 66th minute goal.
"The medical team think it could be quite severe and we hope that is not the scenario, but the way it is looking right now, I think it is going to be a lengthy period of time.
"I think he just went to recover as Moses was raiding for Wigan, and it looked innocuous, but because of the speed the game is played at - he has certainly damaged his Achilles, that is for sure. I just need to find out the extent of it on Thursday when it is looked at properly."