Melbourne, Australia, 20 January 2012 | AAP

So often the last man standing at an Australian Open, Lleyton Hewitt remains upright in the tournament’s third round in defiance of many tipsters.

Hewitt joined Bernard Tomic as the only remaining Australians in the singles draw with a second-round victory on Thursday night after 15th seed Andy Roddick retired with a hamstring injury.

Hewitt held a two sets to one advantage at the time.

Tomic’s credentials as the spear-carrier for Australian tennis will be put to the test on Friday night when he takes on 13th seeded Ukrainian Alexandr Dolgopolov on centre court.

But Hewitt, whose 16th Australian Open is one of very few in which he has not been under pressure to deliver, has reached the third round despite coming off 12 months marred by injury and lacking game time.

The 30-year-old next faces Canadian Milos Raonic on Saturday.

Roddick won the first set on Rod Laver Arena but the match changed complexion when the American stumbled awkwardly during the second – tweaking a hamstring tendon.

Hewitt clambered back into the match taking the second and third sets before Roddick succumbed to the inevitable after two hours and 10 minutes.

“In the last four years I’ve had five surgeries and last year I played just two Grand Slams and two Davis Cup ties,” Hewitt said.

“I came in here with nothing to lose, I’ll play with my heart on my sleeve and see where it gets me.”

Tomic says he’s ready for one of the biggest matches on his career against Dolgopolov – a player who has beaten him three times in the past 12 months on hard courts.

“He seems to play good tennis and bad tennis for a set. So it’s very difficult,” Tomic said.

“You have to just hold your game against him and hope for the best.

“He is a very good player and a lot of people struggle with him.”