Second-seeded Mardy Fish defeated Ricardo Mello 6-2, 6-1 in a matchup of former champions in the second round of the Delray Beach International Tennis Championships on Thursday.
Fish broke Mello's serve in the first and fifth games of the first set and only allowed the Brazilian to hold serve in the opening game of the second.
"I felt great," Fish said. "I couldn't be happier, obviously, with the way it's gone this week."
The American advanced to the quarterfinals where he will play qualifier Alejandro Falla, who beat Adrian Mannarino 6-3, 6-2.
Fish won the Delray title in 2009 and has reached the quarters at least four times. Mello won his lone career title here in 2004.
Del Potro, who was sidelined the whole of 2010 while he healed from a right wrist injury that required surgery, is starting to show the form he reached back in 2009. He's reached the San Jose and Memphis semifinals the past two weeks.
Del Potro never offered Gabashvili a break point opportunity in the match. Gabashvili held serve twice; in the fifth game of the first set and second game of the second set.
"I had a good night and I feel very well," Del Potro said. "I played nice tennis again. I think its a positive that the match was short and Ill have more time to recover for tomorrows match."
The other quarterfinals feature sixth-seeded Janko Tipsarevic of Serbia against Ivan Dodig of Croatia, and 2008 Delray Beach champion Kei Nishikori against qualifier Ryan Sweeting.
The 16th-ranked Fish reached the Memphis semifinals last week and says he's starting to feel better on the court after being diagnosed in November with a thyroid condition that can make him feel lethargic.
Juan Martin del Potro beat Teymuraz Gabashvili 6-1, 6-1
"I certainly go into an event like this feeling like if I'm fit and healthy, and I can sort of play the style of tennis I've been playing the past 10-12 months," Fish said. "I feel like I can win the tournament."