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The Leicester forward has withdrawn from his place on the bench for Wednesday's clash against Wellington, when he will be replaced by his England colleague Richard Hill.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)
Gloucester have been in good form in recent weeks, but Backs Coach Tim Taylor knows that the Cherry and Whites will have to be at their best on Thursday evening (kick off 7:45pm) against a Stade Rochelais side flying high this season.
Speaking to GRTV after the bonus point win over Bristol, back row Lewis Ludlow revealed that despite a tricky first half, Gloucester backed their skills to come through, a faith that was evident in a strong second half showing.
Willi Heinz scored Gloucester's second try as the Cherry and Whites overturned a disappointing first 40 minutes and 0-6 half time deficit, to earn a 26-18 Aviva Premiership victory over Bristol Rugby on Saturday.
It's the first Gloucester-Bristol derby at Kingsholm in over eight years this Saturday (kick off 4:30pm) and, previewing the game with the local media this week, Defence Coach Jonny Bell stressed that, with both teams in the bottom half of the table, they both need the points.
Speaking to the local media this week, Gloucester front rower John Afoa knows the challenge ahead this week against Bristol, and calls on the Cherry and Whites to make the most of home advantage as a determined squad look to bounce back from a narrow loss to Saracens.
Tom Savage speaks to GRTV and the local media as Gloucester went down by 24-20 at Saracens on Sunday afternoon. The second row was disappointed with the result, despite a strong showing from the hosts.
Speaking immediately after the game, skipper Willi Heinz thought that Gloucester had executed their game plan reasonably well and competed hard against Saracens. However, it wasn't enough but the squad will have plenty to work on this week ahead of the derby match against Bristol.
Having named an unchanged starting XV for the past three Aviva Premiership games, Gloucester Rugby ring the changes and retain only five players for Thursday's visit of Stade Rochelais in the European Rugby Challenge Cup (kick off 7:45pm).