Mardy Fish’s time down under is already over. (Nicol As Asfouri/AFP/Getty Images)

But only two days after the Australian Open kicked off in Melbourne, the top-ranked American man in the field is already out of the tournament.

The No. 8-ranked Fish looked frustrated throughout his second round match against unseeded Colombian Alejandro Falla and fell 7-6 (4), 6-3, 7-6 (6).

Uncomfortable and chirpy for much of the match, Fish made 58 unforced errors, including several on critical points after he briefly took a 5-3 lead in the third set. Fish had several openings to claim control of the tiebreaker but sprayed shots wide or long.

The performance was a far cry from his showings last season when the 30-year-old advanced to the third round at the French Open, the Wimbledon quarterfinals and the Rogers Cup final in August. Along the way Fish credited his fitness for helping him grind out long four- and five-set matches.

That endurance was expected to give him an edge in Melbourne where temperatures routinely soar into triple-digits. But at times Wednesdasy, Fish seemed more focused on Falla’s injury timeouts to get treatment for cramping than the match, continuing his complaints during his post-match media session, calling Falla’s tactics “a ploy.”

John Isner was the first American through to the third round after another marathon match. (John Donegan/AP)

With Fish out, only Andy Roddick (15), John Isner (16) and Ryan Sweeting remain in the field to represent the U.S., which also saw youngsters Sam Querrey and Donald Young fall in four sets in Wednesday’s second-round. The tournament opened with 11 American men in the field.

Isner advanced with a grueling five-set victory over David Nalbandian, 4-6, 6-3, 2-6, 7-6 (7), 10-8. The match, which lasted 4 hours, 41 minutes and included a 99-minute fifth set, will test Isner’s recovery ability with a third-round matchup with Feliciano Lopez up next.

Roddick faces Aussie hero and longtime rival Lleyton Hewitt on Thursday while Sweeting will be a heavy underdog against fifth-seeded David Ferrer.

The last American man to reach the semifinals at the tournament was Roddick in 2009. Last year he was again the lone American standing when he lost in the fourth round.

More Australian Open coverage:

Mardy Fish crashes out of Australian Open in second round

Donald Young’s rapid rise hits snag with 2nd-round loss

Roddick cruises in straight-sets 1st-round victory

Australian Open: Schedule of play, match results