Motherwell: Craig Tanner out for up to six months with 'freak' knee injury in training.
The 23-year-old, who has scored nine goals in his debut season at Fir Park, needs surgery on his patella tendon.
"It was a freak incident that happened with nobody near him as he tried a cross-field pass," explained manager Stephen Robinson.
"It's a big blow for us and a big blow for Craig but we'll do everything to make sure he comes back stronger."
Tanner, formerly with Reading, AFC Wimbledon and Plymouth, made his 36th appearance of the campaign in Saturday's loss at Hamilton.
"It's a nasty injury," added Robinson. "His knee cap was out of place and he was in a lot of pain.
"He'll see a specialist by the end of the week but we're looking at a minimum of fourth months (out), more likely to be six.
"It's a disappointment but there are other boys in the squad who maybe haven't quite had the opportunities and it's now for them to step up.