Louis Rees-Zammit in new injury blow.

Wales and Bristol Bears star Louis Rees-Zammit has suffered a new setback after picking up an injury in training.

The 25-year-old sprained his knee during a training session ahead of Bristol's must-win PREM Rugby clash with Gloucester on Friday night and will "return to action in the coming weeks" according to an official medical bulletin from the club.

Rees-Zammit is joined on the sidelines by back rower Steven Luatua, who is out of action until May with a hamstring injury, and Santiago Grondona, who will return to play at the end of the month after suffering a minor calf injury.

The Wales full-back has enjoyed a fine debut campaign for Pat Lam's side after returning from the NFL last summer, but is has not been without setbacks.

After picking up a toe injury against Saracens in October, Rees-Zammit was out of action for over a month before returning in time for Wales' autumn international opener against Argentina.

He then suffered a head blow against Sale at the start of January, which kept him out of action for two weeks as he was pulled from Lam's starting line-up to face the Bulls in South Africa.

Despite this, however, he has featured in 13 games for Bristol in all competitions so far this season, scoring six tries.

Rees-Zammit's absence will be felt as the Bears take on his former side, Gloucester, with Lam admitting his side are now in must-win territory if they are to make the play-offs.

"We have to win if we have any hope of getting to that top four," said the Bristol boss. "There's already a seven-point gap, and everyone plays everyone, but you can't afford to drop any more games. We've only got ourselves to blame for that."

"The season is like life - you get lots of ups and downs - it's how you adapt and grow from that," he added. "We know certainly the game against Gloucester on Friday night is a very important game for us."