But with the game now set to take place tonight, the Crusaders centre, 36, is relieved to get back on the pitch after battling a groin injury to make the game.
"It's good to finally get the go-ahead for the game," said Thomas.
"I'm looking forward to getting back on the field after a few months being injured and I'm especially looking forward to representing my country again."
Thomas led Wales to a Grand Slam in 2005 and then captained the Lions in the absence of Brian O'Driscoll on the tour to New Zealand.
And the charismatic veteran is now focussed on claiming similar achievements in Rugby League.
"Tonight will be good. The real business starts on Sunday in Scotland in our first European Cup game but, for a lot of reasons, the Italy game is very important to me as I need the run out after a few months off," added Thomas.
"We're in the European Cup to win it. The carrot at the end of it, to play in next year's Four Nations against England, Australia and New Zealand is massive. They're the real big guns and the opportunity is something we don't want to miss.
"We want to play against the best. It's all about building Rugby League in Wales and building its profile. If we don't win this then it'll be an unsuccessful campaign, that's why the Italy game is so important for us, so we can prepare for the games ahead."
And Wales coach Iestyn Harris, a fellow Welsh dual-code international, is convinced Thomas will have a big impact.
"Gareth's played 100 games for Wales in Rugby Union so to get the opportunity to play for Wales in Rugby League is something that excites him and something he has a lot of passion and pride about. I'm excited about seeing him play," said Harris, who won 25 caps for Wales at Rugby Union between 2001 and 2004.
"He has made real steady progress in his Rugby League career. He came to Rugby League about five or six games into the Crusaders season and was getting really accomplished in the game before picking up a groin injury.
"Gareth's credentials speak for themselves, particularly in the 15-man code. His experience will be invaluable for us."