"Liam's injury is worse than we feared," Robins boss Gary Johnson told the Bristol Evening Post.
"He went for the scan on Monday and it showed up ligament damage. He will be out for a minimum of three weeks and maybe longer."
Manchester City take on Real Madrid at the Bernabeu for a place in the Champions League final on Wednesday.
Bayern Munich face an uphill battle on Tuesday night when they look to overturn a 1-0 deficit against Atletico Madrid
With the Premier League title sewn up thrillingly by Leicester, attention will soon turn to England's campaign at this summer's European Championship.
The latest gossip and rumours from the newspapers and online:Manchester City have agreed to pay the £39million release clause to
The omens may not look good to some, as Liverpool were beaten convincingly 3-1 by Swansea this weekend whilst second
Leicester have won an improbable title after Tottenham were held to a 2-2 draw at Chelsea to confirm a stunning success this season.