Connacht captain Craig Clarke has been forced to stop playing rugby for "an unspecified number of weeks" after suffering his 10th concussion in 22 months, the most recent in Connacth's 64-6 Heineken Cup defeat to Saracens several weeks ago.

The 30-year-old lock from New Zealand, who has had a huge influence on the Galway side since his arrival, will not play again until further tests have been completed. It means he will miss Connacht’s match against Glasgow on Sunday in the Pro12 with the likelihood of being out much longer.

Due to the nature of the injury Connacht have said Clarke “will be taking some time out.”

At the end of last season Ireland's Luke Marshall took the summer off and missed Ireland's tour to Canada and the United States after suffering three concussions is quick succession. Brian O'Driscoll was also concussed against France in last year's Six Nations championship, while Sean Maitland, the Scotland and Lions winger was replaced against Ireland last Sunday when he was concussed in a collision with Dave Kearney.

“You can just not mess around with that sort of situation. He is a big concern,” said Connacht coach Pat Lam. “At this stage he is going to be unavailable indefinitely, until there is a bit more testing and so forth.”

Lam added that his Connacht squad had been given the week off after their defeat to Saracens but that Clarke continued to suffer symptoms from the head injury.

This year the Six Nations committee introduced the Pitch Side Concussion Assessment (PSCA) for the first time. The PSCA is a tool, introduced by the International Rugby Board, to allow doctors examine players for five minutes if they suspect a concussion has occurred during a match.