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 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:
Australia captain James Horwill says he has been 'vindicated,' after a appeal over an alleged stamp on Wales second row Alun Wyn Jones was dismissed.
He has now been cleared to play in the series decider on Saturday.
Horwill stood on Jones' head in the opening minutes of the first test between the British and Irish Lions and Australia. Jones needed stitches to a wound above his eye.
A disciplinary hearing held 24 hours later concluded that on the balance of probabilities there was no act of foul play. The International Rugby Board announced on Thursday that it was appealing.
Independent appeal officer Graeme Mew upheld the original judgement and said that only a major error during the original hearing would warrant the 'not guilty' verdict being overturned.
Sam Warburton stayed in Melbourne, after Saturday's defeat against the Wallabies, to undergo a scan on his leg.
The Lions have now confirmed that he suffered a 'significant tear in his left hamstring.'
He will remain with the tour party, but will not play in the final test.
Warburton said: "It is incredibly disappointing to be ruled out of the tour through injury as we head to Sydney for the deciding match.
"I wish the team all the best and hope I can play some part in the build up this week. I am confident that the boys can finish the job off and secure the series win."
The British and Irish Lions have confirmed captain Sam Warburton has been ruled out of Saturday's final test after picking up a hamstring injury.