Updated

Tokyo, Japan (SportsNetwork.com) - Top seed Juan Martin del Potro and reigning champion Kei Nishikori were among Tuesday's first-round winners at the Japan Open Tennis Championships.

The former U.S. Open titlist and 2008 Tokyo runner-up del Potro, of Argentina, overcame former Australian Open runner-up Marcos Baghdatis of Cyprus 4-6, 6-4, 6-3, while the fourth-seeded heavy Japanese crowd favorite Nishikori came from behind to beat Austrian Jurgen Melzer 6-7 (4-7), 7-5, 6-2 on a rainy day at Ariake Coliseum. Nishikori beat Canadian Milos Raonic in last year's finale at this hardcourt event.

"I knew drawing Baghdatis in the first round could be the worst match that I could have," said del Potro. "He plays really well on hard courts and I realized his potential. It was a really good match and we both played very well. I really tried to focus to break serve, but Marcos hit a lot of aces and served well."

Last year's Tokyo semifinalist Baghdatis ripped 17 aces in a losing effort against del Potro.

In other action involving seeds, Slovakian lucky-loser Lukas Lacko upended No. 7 South African Kevin Anderson 6-4, 7-6 (7-2) and No. 8 Serb Janko Tipsarevic fought back to best Romanian Victor Hanescu 6-7 (6-8), 6-1, 6-4.

Several other men reached the second round, including Croat Ivan Dodig, Spaniard Feliciano Lopez, and Argentines Horacio Zeballos and Carlos Berlocq, who will face the menacing 6-foot-7 del Potro on Wednesday.