DELRAY BEACH, Fla. (AP) Juan Martin del Potro was tired, sore and still nervous about being back in competition.
The 27-year-old Argentine had reason to celebrate, too, after beating Australian qualifier John-Patrick Smith 6-4, 6-4 on Thursday night to advance to the Delray Beach Open quarterfinals.
Out for 11 months because of a left wrist injury that took two surgeries to repair, Del Potro won consecutive matches for the first time since he reached the quarterfinals in Sydney in January 2015.
Smith attempted to exploit del Potro's backhand, a shot that the Argentine has had to alter from his customary two-hander to a one-handed slice due to the injury. But del Potro was quick enough to run around the backhand and pummel forehands deep into the court.
''I need to improve my backhand as soon as I can,'' said del Potro, the 2009 U.S. Open champion and former world No. 4. ''He kept making me hit backhands down the line and I don't have the confidence to do that.''
Del Potro will face fifth-seeded Jeremy Chardy of France. Chardy fought through swirling wind to beat 19-year-old American wild-card Noah Rubin 6-4, 6-2. Chardy joined fourth-seeded Grigor Dimitrov of Bulgaria as one of only two seeded players left in the draw.
Tim Smyczek set up another quarterfinal against fellow American Sam Querrey.
Smyczek was entered in the qualifying tournament for the event when he learned American teenager Taylor Fritz had earned a special exemption into the main draw by virtue of reaching the semifinals at the ATP event in Memphis last week.
Smyczek was given the wild card instead and he promptly beat Fritz in the first round. He followed with a win over seventh-seeded Donald Young 1-6, 7-6 (2), 6-2 to reach only the second tour-level quarterfinal of his career. The 28-year-old Tampa resident has never reached a semifinal.
Young led Smyczek 6-1, 3-1 before two costly double faults in the sixth game gave the break back.
''I was feeling good mentally even though I was getting my butt kicked,'' said Smyczek. ''I was just trying to figure out a way to disrupt his rhythm.''
Querrey, bolstered by 10 aces, including three in a row at the end of the match, defeated another American, Austin Krajicek, 6-4, 6-3.