Ulster have revealed that Luke Marshall has suffered yet another concussion-related injury in training.

The centre is currently following the return to play protocols, but he looks unlikely to be fit for this weekend's Champions Cup match against Toulon.

Marshall sustained four concussions between March 2013 and February 2014.

Dan Tuohy has also been ruled out with a thumb injury, which will require surgery to repair and is set to keep him out for up to eight weeks.

Prop Wiehahn Herbst picked up a hamstring injury against Treviso last weekend and will also miss Saturday's trip to the south of France.