England back Jonny May is facing a race against time to be fit for the new Aviva Premiership season.
The Gloucester player made his international debut on the summer tour of Argentina but suffered a knock to an elbow during a pre-season fixture against European champions Toulon on Friday.
May's teammate Shane Monahan was also injured during the match in France, hurting a shoulder as Gloucester lost 42-17.
Gloucester's rugby director Nigel Davies told the club's official website: "We will just have to wait and see what kind of timescale we're looking at for both.
"They will be assessed further this week and we will take it forward from there.
"But I think it is fair to say neither injury will be short-term. It is disappointing to pick up injuries, especially at this stage of proceedings.
"They have both looked sharp in training, and they showed up well out there on Friday.
"So it's hugely frustrating for them after working so hard in the pre-season up to this point and being ready to get going in matches."
Gloucester begin their Premiership campaign with a home match at Kingsholm against Sale Sharks on September 7.