The British and Irish Lions have been hit by a potential double injury blow ahead of next Saturday's second Test against Australia in Melbourne.
The Lions announced that lock Paul O'Connell and prop Alex Corbisiero are being "treated and assessed" for arm and calf muscle injuries respectively.
Ireland prop Tom Court, meanwhile, has been called into the squad and will go straight onto the replacements' bench for Tuesday's game against the Melbourne Rebels.
Ulster forward Court is currently in his home city Brisbane following Ireland's North American tour, and he will join up with the Lions squad tomorrow.
Corbisiero, who joined the Lions tour as front-row cover earlier this month from England's two-Test trip to Argentina, went off early in the second half as the Lions beat Australia 23-21 at Suncorp Stadium yesterday.
Mako Vunipola - a probable second Test starter if Corbisiero is ruled out - has been withdrawn from the match-day 23 for the Rebels clash.
O'Connell's injury, meanwhile, must be of huge concern to the Lions.
The 33-year-old second-row talisman has featured in seven Lions Tests and was the 2009 tour captain in South Africa. He has won 85 caps.
He is an integral part of coach Warren Gatland's plans, and if he is ruled out of the Test series then it would represent a colossal blow.
Should O'Connell not make the second Test, then England and Leicester lock Geoff Parling would be favourite to replace him, partnering Alun-Wyn Jones in the second row.
The Lions initially looked to have emerged trouble-free from a bruising opening Test - unlike their opponents.
Australia saw three backs - Berrick Barnes, Pat McCabe and Christian Leali'ifano - carried off, and they played the final 30 minutes with flanker Michael Hooper in midfield.
Three players, including veteran back-row forward George Smith, were today called into their squad.
But it now appears that Corbisiero and O'Connell are both struggling for Melbourne.
On the other side of the coin, centres Manu Tuilagi and Jamie Roberts are in contention to make it after recovering from respective shoulder and hamstring injuries, along with wing Tommy Bowe, who has recovered rapidly after suffering a broken hand against Queensland Reds 15 days ago.
Reflecting on the encouraging comebacks of Bowe and Tuilagi, Gatland said: "To have Tommy and Manu fit and back is a great compliment to the medical staff.
"Tommy is fit for Saturday, he's running, but the more time he has to heal the better.
"The surgeon said that that injury is normally a six to eight-week injury, so to be fit in three weeks is magnificent. It's important not to risk him on Tuesday.
"We don't think Jamie is too far away, he's up and running and is potentially available for next weekend."
Australia face an anxious week as they assess injuries to McCabe (neck), wing Digby Ioane (shoulder), Leali'ifano (concussion), Adam Ashley-Cooper (shoulder) and Barnes (head knock).
Reinforcements have been added to their squad in the form of Smith, full-back Jesse Mogg and centre Ben Tapuai.
Parling, whose wife Elle gave birth to a daughter May on Thursday, will lead the Lions against the Rebels at AAMI Park on Tuesday.
Parling takes the captaincy from Rory Best, who drops to the bench following his poor performance in last week's 14-12 defeat by the Brumbies in Canberra - the Lions' only loss in seven matches on tour.
"It's obviously a great honour, and I am looking forward to getting some more game time. A few of the boys have a point to prove and are keen to start," Parling said.
Gatland admitted there were shortcomings in the Lions' performance at Suncorp Stadium, adding: "We know the performance wasn't brilliant, but it's all about the result.
"For both sides it was about sparring, finding out information about each other."