The Lions lost their captain Sam Warburton on Monday, less than 48 hours after the Welsh flanker turned in one of the heroic performances of the tour in attempting to resist the Wallabies as they levelled things up at one Test apiece in Melbourne. As they received confirmation of the news they had been dreading, the visitors were wondering whether they had lost the series into the bargain.

Warburton’s hamstring injury – a significant tear of the muscle, according to the Lions medic Dr Eanna Falvey – is a grievous blow. The Cardiff Blues player described this dark development as “ incredibly disappointing”, and while there was no immediate comment from the Lions hierarchy, they would rather have heard that the world was about to end.

Warren Gatland, the head coach, chose the openside specialist as leader ahead of more experienced candidates, including the Irish stalwarts Brian O’Driscoll and Paul O’Connell, because he knew how influential he would be when the chips were down.

After suffering the injury midway through the final quarter of Saturday’s narrow defeat at the Docklands Stadium – he had just produced 60-odd minutes of the most committed back-row play imaginable – the Welshman stayed behind in Melbourne for a scan while the rest of the squad flew to the Queensland coast for a brief spell of relaxation. The scan results were grim. There was some suggestion on Monday that his recovery time would be measured in months rather than weeks.

His absence from this weekend’s final Test in Sydney, where the Australians are likely to start as firm favourites, will inevitably lead to a strategic and tactical rethink by Gatland and his fellow coaches. They could simply replace him with another Welsh breakaway, Justin Tipuric of Ospreys, whose form has been strong during the tour, albeit against weak opposition. But equally, the selectors could decide Warburton’s withdrawal demands a root-and-branch reconsideration of the options at loose forward.

It is well known that Warburton is happiest when playing alongside the hard-tackling Wales blindside specialist Dan Lydiate: indeed, the two of them were paired in Melbourne as Gatland went in search of the victory that would have brought the Lions a first series triumph in 16 years. But the downside of that selection became clear at the line-out, where the demotion of the England flanker Tom Croft to the bench was felt most acutely, the set-piece duly going pear-shaped. Does Warburton’s misfortune automatically obviate the need for the workaholic Lydiate? This will be discussed, at length.

Leading on from this, might Croft’s reappearance in the starting back row signal the end of the road for the Irish No 8 Jamie Heaslip, whose form at Test level has been underwhelming at best? A flank combination of Croft and Tipuric would cry out for Toby Faletau of Wales in the central position: a No 8 who plays in prose rather than poetry, but makes more than his fair share of hard yards with ball in hand. If the coaches choose to reject the claims of Tipuric, the versatile Irish forward Sean O’Brien will perform the fetching duties in the No 7 shirt.

There are several other selectorial conundrums to be solved by Gatland and company: in fact, there could  ultimately be changes in each row of the scrum, at half-back and in midfield. Not all of these potential switches can be laid at the door of Warburton’s dodgy hamstring, but it is certainly the case that his sudden disappearance has prompted a  serious debate in all sorts of areas.

While the Lions were feeling sorry for themselves on the Sunshine Coast – a name wholly out of sync with the current desperate weather conditions – the Wallabies were doing everything in their power to keep their own captain, the outstanding lock James Horwill, in contention for the Sydney date. The Queenslander was yesterday re-tried on a charge of stamping on the head of his rival second-rower, Alun Wyn Jones, during the first Test in Brisbane, having been cleared of the offence, somewhat unfathomably, in the original hearing a little over a week ago.

Following an appeal by the International Rugby Board, which has been made to look more than a little ridiculous in recent days, a new judicial officer, Graeme Mew, who holds Canadian and British passports, conducted the hearing via video link and was considering his verdict when Horwill headed for bed. Understandably, given that this is Test week and the Wallaby backs James O’Connor and Kurtley Beale have already landed themselves in a small ocean of hot water during this series for staying up until silly o’clock while on international duty, the Australians were in no hurry to interrupt their skipper’s sleep with news of the decision. His chances of playing in Sydney remained in the balance as Mew sifted the evidence.

Should the Wallabies lose Horwill, they will feel as much pain as the Lions are feeling over Warburton. The lock holds a fragile Australian pack together. With the scrum-half Will Genia, he is the man the home side cannot hope to replace. If the Lions were frustrated to see him on the field in Melbourne – they felt the video footage of the Jones incident had him bang to rights – they will be really hacked off of if he trots out again this weekend.

Limping lions: Onjury update

Alex Corbisiero

Loosehead prop injured a calf in first Test victory and was ruled out of second Test defeat but now back in contention

Jamie Roberts

Centre is raring to go for decider after missing first two Tests with hamstring injured in warm-up victory against the Waratahs.

Sam Warburton

Captain injured his left hamstring during the second Test defeat. Flanker is ruled out of the final Test.

Mike Phillips

Scrum-half has been struggling with a knee injury on tour. Had an ‘inflammation injection’ to cure the problem.

Paul O’Connell

Lock ruled out of the rest of the series after fracturing his arm.

Cian Healy

Prop was forced to leave the tour with an ankle injury.

Gethin Jenkins

Prop also withdrew from the tour after sustaining a calf injury.