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The Leicester forward has withdrawn from his place on the bench for Wednesday's clash against Wellington, when he will be replaced by his England colleague Richard Hill.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)
Tom Marshall scored his first Gloucester try in the 31-23 win over Saracens on Friday evening and was named Man of the Match. Talking to GRTV, he praised the forwards for setting the tone on the night.
Matt Scott was on media duty this week, and the Scottish international spoke about the benefit of having a full week of training with his club mates and the determination to get back to performing well against Saracens this Friday evening.
After the disappointment of last weekend's performance at Leicester, Director of Rugby David Humphreys told GRTV that he expects a big response from Gloucester in Friday's Aviva Premiership fixture at home to Saracens (kick off 7:45pm).
Gloucester travel to Tigers this Saturday in good spirits, and fly half Billy Burns is looking forward to testing himself in one of the toughest environments in the league as the Cherry and White hunt vital points as attention returns to the Aviva Premiership
Gloucester's Ciaran Knight made his first start at tighthead prop, Henry Walker made his first appearance as a second half replacement and Alex Seville also featured as England U20s might it three from three in the U20s Six Nations with a 46-0 win over Italy in Darlington on Friday night.
Mental health and wellbeing is just as important as physical health, which is why the Gloucester Rugby Community team have partnered with Public Health Gloucestershire to become Mental Health First Aiders.