Tomic had just dropped the first set 6-4 to the world No.1 when he called it a night.

The 21-year-old first complained of the injury very early on and the writing was on the wall when he sought a medical timeout after just three games to have treatment.

He complained of having difficulty pushing off on his left leg, but emerged a few minutes later with his left thigh strapped.

Feeling uncomfortable, Tomic discarded the strapping shortly and managed to keep pace with Nadal until the ninth game.

Facing his first break-point, Tomic pushed a forehand wide to drop serve and fall behind 5-4.

Nadal consolidated the break to clinch the set after 42 minutes when Tomic sliced a backhand into the net.

Tomic advised the umpire at the changeover that he was unable to play on, drawing boos from sections of the crowd at Rod Laver Arena.

"I just want to say I'm sorry for Bernard," Nadal said. "I hope he gets better very soon."

Meanwhile, Australian tennis teens Nick Kyrgios and Thanasi Kokkinakis have continued their seamless transition to the senior ranks, advancing to the second round.

Kyrgios was first into round two, putting experienced German Benjamin Becker to the sword.

After receiving treatment for an ongoing shoulder problem in the fourth set, Kyrgios came from a break down to win 6-3, 6-7 (5-7), 6-2, 7-6 (7-2), and set up a second-round clash with Frenchman Benoit Paire, the No.27 seed.

South Australian Kokkinakis, 17, showed he was also up to task in his grand slam debut as he overcame leg cramps to oust world No.73 Dutchman Igor Sijsling 7-6 (7-4), 0-6, 7-6 (7-3), 6-2.

He will next face Rafael Nadal.

Victorian Olivia Rogowska also joined the pair on the winners' list, tasting success at Melbourne Park for only the second time in six attempts with a 6-3, 6-3, victory over Colombia's Mariana Duque-Marino.

Playing in a record 18th Australian Open, tennis warrior Lleyton Hewitt narrowly failed to conjure up another five-set miracle, going down 7-6 (7-4), 6-3, 5-7, 5-7, 7-5, to No.24 seed Andreas Seppi. Former world No.1 Hewitt squandered one match-point in the tight final set against the Italian.