Jones was on the replacements bench for the Scarlets at the time Ireland scrum-half fractured his left ankle early in the Magners League clash at Munster's Musgrave Park and he admits he was saddened by his would-be team-mate's withdrawal from Ian McGeechan's touring party.
However, despite watching O'Leary's Lions dream end first hand, the 32-year-old Welsh international says he and the rest of McGeechan's 2009 Lions choices have to put the unfortunate incident to the back of their minds in the build up to the tour.
"It's disappointing for Tomas and I really feel for him," said Jones, who will be embarking on his second successive Lions tour and looking to add to his three previous Test caps when the Lions arrive in South Africa.
"He's been fantastic this season and it's a sad loss for the Lions.
"But we have to be professional and play the remaining games with a strong mindset. Rugby is a contact sport and it's inevitable injuries will happen."
Meanwhile, Scarlets' chief executive Stuart Gallacher has attempted to reassure the Parc-y-Scarlets faithful that their star playmaker will still be at the region when he returns from Lions duty in July.
Gallacher has dismissed a Sunday newspaper report that Jones will be departing the West Wales region for the second time in five years having only returned from French outfit Clermont Auvergne in 2006.
"It is totally unsubstantiated and is complete rubbish," said Gallacher.
"I've spoken to Stephen Jones today and he wishes to convey quite categorically that he has not spoken to any other club and has no intention of doing so - and that he will be staying with the Scarlets next season.
"He has a three-year contract with us until the end of the 2009-10 season and we look forward to working with him going forward on a fresh campaign next season.
"Stephen Jones is a world-class player and one that this club and its supporters have enormous respect for. He is a Scarlet through and through and has been with us for many years.
"He understands this region, has great pride in its history, ethos and values and will continue to make a major contribution to the Scarlets squad going forward as he has done this season as vice-captain.
"We're delighted that he has been selected again for the Lions; he thoroughly deserves his place on the tour and I know he is looking forward to the campaign in South Africa."