Last updated on .From the section Scottish Premiership

David Turnbull scored 15 goals in 31 appearances last season

David Turnbull's £3.25m move to Celtic from Motherwell has collapsed after it emerged that the midfielder needs "immediate preventative" knee surgery.

The clubs had been in talks after the deal was delayed following a medical and after a four-year deal was agreed.

Motherwell say Celtic were still keen to sign Turnbull, 19, but that terms could not be struck after the Scottish champions submitted a revised offer.

Turnbull will now have an operation and will be out for "an extended period".

"We will give David all the support he needs during this process," read a statement from the Fir Park club.

"We wish him the best with his procedure and rehabilitation, and look forward to watching him play in claret and amber again in the near future."

Celtic responded by releasing a statement of their own, describing the outcome as "unfortunate" and thanking both Motherwell and Turnbull.

'It is regrettable David will be out of action for a considerable length of time and, clearly, these circumstances are totally outwith the club's control. We did everything we could to find a solution," they said.

The transfer saga started on 12 June when Motherwell and Celtic agreed on a fee.

A Norwich City offer matching that was also accepted by the Fir Park club, but Turnbull chose the treble treble winners after talks with the Premier League outfit.

After initial terms were offered and then rejected, Celtic removed themselves from the running as Norwich made their move. However, a new bid from Parkhead was enough to convince Scottish Football Writers' young player of the year Turnbull to pick Celtic.

During his breakthrough season at Fir Park, the midfielder scored 15 times and earned two Scotland Under-21 caps.

'You can't really fail a medical' - analysis

Agent and former footballer Allan Preston on BBC Radio Scotland

A medical can actually vary whatever club you're at. The higher up you go, the more millions of pounds that are getting spent, the more thorough it will be. You can't really fail a medical. It's not really a pass or fail.

When you get CT scans, that can certainly highlight if there's a problem in your knee or your ankle or your back or anything at all. It's just a doctor's opinion. It's a recommendation and then it's up to that club to act on that information.