Flushing Meadows, NY (My Sportsbook) - Battling a sore back, fifth-seeded Englishman Tim Henman needed all five sets Tuesday to sneak past big Croat Ivo Karlovic in the opening round of the U.S. Open. Meanwhile, former champion Marat Safin of Russia was a disappointing first-round loser on Day 2 at the year's final Grand Slam event.

Henman, who injured his back while practicing over the weekend, edged out the 6-foot-10 Karlovic 7-6 (7-3), 6-7 (7-9), 4-6, 6-4, 6-4 in 3 hours, 37 minutes at Armstrong Stadium on the grounds of the USTA National Tennis Center. The Brit advanced with the help of three breaks, as Karlovic possesses one of the biggest service games on the men's tour.

Karlovic launched 39 aces at Henman, but the big Croat also piled up 13 double faults and 54 unforced errors, as Henman prevailed despite striking 53 fewer winners (123-70) than his tall counterpart.

Up next for the French Open semifinalist Henman will be Frenchman Jerome Golmard.

The 13th-seeded Safin appeared listless in a 7-6 (7-5), 6-4, 3-6, 6-3 defeat at the hands of former top-10 player Thomas Enqvist of Sweden.

The 24-year-old Safin seemingly led the way on the stats sheet, firing more aces (17-10), committing fewer double faults (2-12) and unforced errors (54-56) and compiling more winners (57-54), but Enqvist was there on the biggest points and broke Safin's big serve on five occasions, compared to four breaks for the hot-headed Russian.

Safin captured the 2000 U.S. Open by whipping the legendary Pete Sampras in the final here and is a two-time Australian Open runner-up, including earlier this year against Swiss star Roger Federer.

Tenth-seeded Olympic gold medalist Nicolas Massu of Chile reached the second round by pasting Argentine Jose Acasuso 6-4, 6-0, 6-2. The gritty Massu captured both men's singles and doubles gold in Athens less than two weeks ago.

Other seeded winners were No. 15 Paradorn Srichaphan of Thailand, No. 18 Tommy Robredo of Spain and No. 22 Dominik Hrbaty of Slovakia.

Others advancing to the round of 64 were Austrian Alexander Peya, Russian Dmitry Tursunov, Korean Hyung-Taik Lee, Frenchman Michael Llodra, Spaniard Alberto Martin, American Paul Goldstein and German Florian Mayer.