Nishikori, Haas, Hewitt advance at ATP Delray Beach
Japan's Kei Nishikori, pictured during a Davis Cup match in Tokyo, on February 2, 2014 - by Toshifumi Kitamura
Third seed Nishikori on Tuesday surrendered seven double faults but won six of his 13 break-point chances and dropping his serve only three times against the 23-year-old from Portugal over one hour and 55 minutes.
Nishikori, ranked 15th, will next face 65th-rated Russian Teymuraz Gabashvili, who rallied to eliminate Australian Matthew Ebden 2-6, 6-3, 6-2.
Top seed Tommy Haas and eighth seed Lleyton Hewitt breezed into the second round.
World number 12 Haas, a 35-year-old German who won the event in 2006, needed only 55 minutes to eliminate US qualifier Wayne Odesnik 6-2, 6-1 while 32-year-old Aussie Hewitt, cheered on by countryman and golf legend Greg Norman, took 65 minutes to oust American Bradley Klahn 6-3, 6-1.
"It's always tough to find rhythm here," said Haas. "And it's a bit windy so it's a bit tricky. You go there and try to really focus down on your game plan and I think I did just that. I'm really proud of the game plan I had and executed well on that."
Haas' win secured a second-round match against US qualifier Steve Johnson, who defeated Kazak Mikhail Kukushkin 6-4, 6-3.
Hewitt, who now has 598 ATP match wins, will next face fellow Aussie Marinko Matosevic, who downed Belgian David Goffin 6-2, 6-4.
Taiwan's Lu, meanwhile, who was coming off a retirement due to a neck injury in a Memphis semi-final against Croatian Ivo Karlovic, won his first set 6-4 but retired against Ryan Harrison after the American held serve to open the second set Tuesday.
South African fourth seed Kevin Anderson, who lives in Delray Beach, reached the second round by fighting back to beat American Tim Smyczek 4-6, 6-1, 6-3.
Next in Anderson's path is Karlovic, who opened with a 7-6 (7/4), 6-3 victory over Aussie lucky loser Samuel Groth.