A calf injury means Canadian prop Exner will not join the Pirates (Getty)

A serious calf injury has forced the Cornish pirates to call-off the signing of Canadian prop Iain Exner.

He was due to have joined from French club Pau along with Bertrand Bedes and Michael Burak but will be out for up to six months with the calf problem.

"With regret we have decided that we will not be able to offer him employment with the Cornish Pirates next season," said CEO Ron Coward.

"Iain fully understands and accepts our decision," the chief executive added.

"He has returned home to Canada where hopefully he will enjoy a full recovery from his injury."

The club said they were now negotiating to bring in a suitable replacement for Exner in the near future.

Exner, 29, is a former Canada international who toured New Zealand with his country in 2006.