Lions flanker Lewis Moody faces a race against time to be fit for first Test contention against New Zealand next week.
The Leicester forward has withdrawn from his place on the bench for Wednesday's clash against Wellington, when he will be replaced by his England colleague Richard Hill.
The Lions confirmed Moody had suffered an injury to his left knee in training, but the apparent seriousness was not revealed until coach Gareth Jenkins spoke to the media in Wellington on Tuesday.
Jenkins revealed that Moody is "out of the selection process" for next Saturday's game against Otago in Dunedin, and that will seriously hamper his Test prospects, given the Lions boss Sir Clive Woodward is likely to have finalised his first choice line-up by early next week.
Moody has not travelled to Wellington, remaining behind at the squad's Christchurch base for further tests.
Three players - Lawrence Dallaglio, Malcolm O'Kelly and Simon Taylor - have already been ruled out of the tour because of injuries.
The possible loss of Moody would be a huge blow, given his versatility at blindside and openside flanker, but it would appear the signs are not good.
Prop Andrew Sheridan, meanwhile, is battling to overcome an ankle injury sustained against the New Zealand Maori last Saturday, raising doubts about his prospects of being fit to face Otago. Like Moody, Sheridan is a serious candidate for the Lions' Test 22.
The British and Irish Lions team to play Wellington on Wednesday is:
J Lewsey (Wasps and England); J Robinson (Sale and England), B O'Driscoll (Leinster and Ireland, capt), G Henson (Ospreys and Wales), G Thomas (Toulouse and Wales); J Wilkinson (Newcastle and England), D Peel (Lanelli and Wales); G Jenkins (Cardiff and Wales), S Byrne (Leinster and Ireland), J White (Leicester and England), D Grewcock (Bath and England), B Kay (Leicester and England), S Easterby (Llanelli and Ireland), N Back (Leicester and England), M Corry (Leicester and England).
Replacements: G Bulloch (Leeds and Scotland), M Stevens (Bath and England), P O'Connell (Munster and Ireland), R Hill (Saracens and England), C Cusiter (Borders and Scotland), S Jones (Clermont Auvergne and Wales), S Horgan (Leinster and Ireland)
Skipper Billy Twelvetrees told GRTV after the win in Brive that the game could have been a tough one to get up for, but that his Gloucester team mates did themselves proud on the night and got a big result.
Reflecting on the 31-20 victory in Brive on Thursday evening, Director of Rugby David Humphreys said that clinching a home European Rugby Challenge Cup quarter-final was the overall aim and duly achieved.
Gloucester may have already clinched a home European Rugby Challenge Cup quarter-final, but Director of Rugby David Humphreys wants his side to finish the pool stages on a winning note in Brive on Thursday evening.
Speaking after Saturday's win, James Hudson was happy to record a bonus-point win against a hugely physical Oyonnax side as Gloucester secured their passage into the European Rugby Challenge Cup Quarter Finals
Billy Burns was a try scorer on his first European start for Gloucester and, speaking after the game, admitted that it was good to get the five points although there are still things to work on before the trip to Brive.
Gloucester Rugby have added to their front row strength in depth for next season with the signings of Paul Doran-Jones, Paddy McAllister and Nicky Thomas from Harlequins, Aurillac and the Ospreys respectively.