Canadian sensation Milos Raonic is up for one of his biggest challenges in his young tennis career as he faces Olympic tennis champ Andy Murray at the U.S. Open in fourth round action Monday at 7:30 p.m.

And although Raonic might be the underdog, he managed to beat Murray in their only head-to-head meeting, on clay at the Barcelona Open earlier this year where Raonic posted a stunning 6-4, 7-6 (3) victory.

It will be different on the hardcourts of Flushing Meadows, which favour Murray's all-round game. While the Scot hasn't won a Grand Slam yet, he has reached a U.S. Open final and has twice been a finalist at the Australian Open, which is also a hardcourt event.

However, Raonic's greatest weapon is his serve, which will be more dangerous on the fast hardcourt than on the deadening clay of Barcelona.

"I think I'm just going to have to really go for it and go after him and try to control as much as I can," he said. "I think on the hardcourt I'll have more opportunities to do so, and I feel if I do that and I serve well then I'll definitely have my opportunities."

Early at Flushing Meadows it looked like Raonic may not even get to this point. The tournament's 15th seed from Thornhill, Ont., struggled mightily in the first round in a five-set win over world No. 46 Santiago Giraldo.

He recovered impressively and won his next two games in straight sets with his powerful serve, firing 30 aces in his second-round win over Paul-Henri Mathieu and 29 in his third-round victory over James Blake.

"I definitely struggled early in this tournament. It was lucky to get by the first one," Raonic said Sunday on a conference call from New York. "Then I got better in the second round and I felt I started to play really well.

"(The confidence) is definitely building up at the same time as my game. I'm doing more and more things I want to be doing and my serve's helping me a lot with that."

A win against Murray would put Raonic in a semifinal against either 12th-seeded Marin Cilic or unseeded Martin Klizan, giving him a realistic to advance to a possible semifinal match with top-ranked Roger Federer.

Andy Murray is wary of Raonic's big serve, it would seem.

"Raonic has a huge serve, he's leading the tour in aces this year," said Murray, 25 at a press conference.

"He's a big, strong guy and I just need to bring my return game for the next round."

-With a file from The Canadian Press