The British and Irish Lions coach Warren Gatland said the "head overruled the heart" on many of his selection decisions for the final test against Australia in Sydney.
Former Lions captain Brian O'Driscoll said he was "totally gutted" at being left out of the squad for the decisive match this Saturday.
Gatland said: "Picking this team was not easy and ultimately with several players available after recovering from injury the head overruled the heart in many selection decisions.
"Brian O'Driscoll is a great player and has had a wonderful career but for the final test in Sydney, we just felt Jamie Roberts' presence offered us something more".
Former Australian Rugby Union legend David Campese and current player Matt Giteau have criticised the British and Irish Lions' decision to drop Brian O'Driscoll.
Lions team info. Sorry but you have just handed to series to Australia. 7 chances and still no real match winner
Gee dropping @brianodriscoll out of the team is a huge call.. For mine, he has been the stand out unsung hero this series.. Defensively huge
However, former England player Jeremy Guscott praised Warren Gatland's "bold and brave selection".
Well done WG, bold and brave selection that was required to beat this improving Aussie team
Former Lions captain Brian O'Driscoll has said he is "totally gutted" at being left out of the squad for the final and decisive Test against Australia:
Obviously totally gutted at being left out for deciding Test but all efforts go into preparing the boys to see it through. #seaofred
The British and Irish Lions captain Sam Warburton will miss the series-deciding third test against Australia in Sydney after suffering a "significant" hamstring tear.
The Welsh loose forward sustained the injury late in Saturday's 16-15 second test defeat in Melbourne, which has left the series at 1-1 before Saturday's Sydney showdown.
The Lions said on their official Twitter feed: "The British & Irish Lions confirmed today that captain Sam Warburton would play no further part in the tour after suffering an injury during the second test.
"He will remain with the tour party for the third test in Sydney on Saturday."
The British and Irish Lions face a series decider in Sydney next Saturday after falling short 16-15 in a tight second Test against Australia at the Etihad Stadium in Melbourne.
5mins to K/O people! Who's excited?! 12 years of waiting has come down to just 80mins. This will certainly be a night to remember #AUSvLIO