Sexton is the odds on favourite for the Lions fly-half berth this summer and Biggar knows that facing the Leinster playmaker will present a massive challenge at the Millennium Stadium.
"I could sit here all day and say how good a player Sexton is," said Biggar, who will win his 12th cap in the Cardiff opener.
"I'm really looking forward to going up against him. I have played against him many times, and he's right up there on top of his game at the minute.
"It's a real challenge and privilege to play against him when he's playing as well as he is.
"He's a great player and he's got great players around him, which is always nice for a 10. It makes your job easier when you've got centres like (Gordon) D'Arcy and (Brian) O'Driscoll outside you.
"But we have got a pretty good back line with the likes of Jamie Roberts and Jonathan Davies. They have got pedigree as well."
Sexton may appear to have the starting spot for the Lions sewn up but Biggar's elevation to first-choice for his country presents a major opportunity for the 23-year-old to impress.
With Lions head coach Warren Gatland set to name his touring party in late April, a strong Six Nations could put Biggar firmly in the mix for a spot Down Under.
But the prospect of a first Lions adventure brings extra pressure to a position already filled with expectation within Wales given the rich history the nation has of producing world-class outside-halves.
It's a pressure that Biggar refreshingly admits he is aware of but one that he insists he accepts as part of his promotion.
"I don't think there is any hiding my international career has been a bit stop-start and I hope to get it going this weekend against a good Irish side," added Biggar.
"The Six Nations tournament is the best in the world and it's something I'm really looking forward to.
"I would like to think it's my best opportunity to put a marker down and go from there.
"There's a lot of pressure, it is part of the job title. It's a difficult position to be in. So I could give you the routine answer of 'you just get on with it and you don't pay any attention to it'... but of course you do.
"You are aware of the Welsh 10 jersey and the expectation around it. As a player, when your team is playing well, it's a great position to be in, but when things aren't going quite as well as you would perhaps have liked, that's when you come under scrutiny.
"As a 10, especially in Wales, that's part and parcel of the job. You have to take it as it comes, but you also have to enjoy the high bits as well, when you are playing well and winning."