Henry Paul will miss the remainder of the season after Gloucester's medical team confirmed he has damaged the medial ligament in his knee.
The England international injured his knee playing for England Sevens at the World Cup in Hong Kong 10 days ago and was ruled out of last Saturday's win over London Irish.
Paul is set to be out for between six and eight weeks and will be unavailable for Gloucester's final three Zurich Premiership games, and any play-off matches.
Commenting on www.gloucesterrugbyclub.com Melville said: "It's a set-back but in some ways sums up our season. We have just had so many people injured at crucial periods, but you only have to look around the Premiership to see that other clubs are in a similar situation."
Commenting on www.gloucesterrugbyclub.com Paul added: "It's a big disappointment. I'm concentrating on getting back to full fitness, and will be right behind the rest of the team as we push for the top three slot in the Premiership and next season's Heineken Cup."
Paul, who has missed only a handful of games in four seasons with Gloucester, will see a specialist next week who will assess whether an operation is required.
Despite the injury, Nigel Melville's fly-half options could be boosted for Gloucester's next Premiership game at home to Leeds Tykes on Saturday 9 April with the return of Duncan McRae.
The Aussie stand-off has had an injury hit season, with his most recent knee injury ruling him out since the defeat away at Quins at the beginning of February.
As well as McRae's possible return, 22 year-old Brad Davies, who played the full 80 minutes at number 10 for Gloucester in the 13-12 win over London Irish on Saturday, was in commanding form for Gloucester against the Exiles at the weekend.
Speaking to the local media this week, Richard Hibbard expressed his excitement ahead of the West Country derby and that there is an extra spring in the step of the Cherry and Whites ahead of the tough challenge.
With such a short turnaround between the two games, and Gloucester looking to reintegrate several players into the line-up after the Autumn international series, Tom Savage told GRTV that the Cherry and Whites will keep changes to a minimum for the European Rugby Challenge Cup game in Zebre on Saturday.
Gloucester travel to Italy this weekend to take on Zebre in Round Four of the European Rugby Challenge Cup. The Cherry and Whites defeated the Italian side 35-10 last Sunday, but Director of Rugby David Humphreys is looking for an improved performance in the return fixture.
Skipper Billy Twelvetrees, speaking to GRTV after the 35-10 over Zebre, was happy with the bonus point win over the Italian side but admitted Gloucester will need to tighten up for the return fixture in Parma.
Gloucester Rugby welcome Sione Kalamafoni, Greig Laidlaw and Tom Palmer back to the starting line up and feature David Halaifonua in a matchday squad for the first time, as they resume Aviva Premiership action against Bath Rugby at Kingsholm on Saturday (kick off 5:30pm).