Australian Open - - US Open Champion Juan Martin del Potro Survived 5-Set Second Round Match Against James Blake

Reigning US Open champion Juan Martin del Potro survived an epic five-set match against American James Blake to move into the third round of the Australian Open.

The 21-year-old fourth seed had to rally from behind to overcome his older rival 6-4 6-7 (3/7) 5-7 6-3 10-8 in a match that lasted four hours and 17 minutes under the Hisense Arena lights.

Del Potro's fellow top seeds enjoyed far easier paths through, with defending champion Rafael Nadal, fifth seed Andy Murray and seventh seed Andy Roddick winning in straight sets.

Both players finished an energy-sapping encounter suffering with cramp before Del Potro sealed the match in the 18th game of the fifth set with a forehand down the line.

It was hard on Blake, who was forced to back up less than 24 hours after playing his rain-delayed first-round match. "It was tough for him, playing two days in a row and this five-set match," Del Potro sympathised, having had a day's extra rest following his first-round win over Michael Russell on Monday.

"Of course, it is difficult. Maybe I had a little luck because I played on Monday in not too long of a match. (But) it was a good match. It was very difficult to keep trying and keep going. You have to be focused every point, every time, and try to take your chance. I had my chance in the last set."

Seventh seed Andy Roddick side-stepped Brazilian Thomaz Bellucci 6-3 6-4 6-4 without much fuss and next in his way is Feliciano Lopez after the Spaniard beat 2003 finalist Rainer Schuettler 6-3 2-6 6-3 6-2.

Fernando Gonzalez, the 2007 winner, and Gael Monfils both won for the second day running.

Only two seeds fell on Wednesday, with Tomas Berdych (21) bundled out by Kazakhstan's Evgeny Korolev 6-4 6-4 7-5. Serbian Viktor Troicki (29) was also eliminated 4-6 6-4 7-6 (7/2) 6-1 by Florian Mayer, who was rewarded with a third-round match against Del Potro.

In the last match of the day, 14th seed Marin Cilic was taken the distance by Australian teenager Bernard Tomic 6-7 (6/8) 6-3 4-6 6-2 6-4, with play not finishing until after 2am.