Defending champion Xavier Malisse and second-seeded Tommy Haas were ousted in the first round of the Delray Beach International on Monday.
Both Haas and Malisse arrived at the tournament coming off medical issues.
The No. 27-ranked Haas, who lost to Diego Hartfield of Argentina 6-2, 3-6, 6-2, was playing in his first match of the year after having a third surgical procedure on his right shoulder in mid-November.
"When you have surgery you hope it goes well," Haas said. "Overall, it feels pretty good. This is my first test. I started playing a lot more tennis the last 10 days and overall, I'm kind of happy with how I played."
Malisse, who played in only five tournaments last year because of a right wrist injury, was ousted by American Bobby Reynolds 6-2, 4-6, 6-3.
For Haas, 29, there seems to be a possibility that his playing days might be nearing an end.
"It's a tough game, but I love it so I'm trying to come back and see how it goes," Haas said. "Many times I want to throw in the towel and maybe retire. I consider myself pretty young, so I'm going to try and see what this game brings to me."
Haas couldn't find his competitive edge in the opening set, but managed to muddle his way through to win a tough second set where the games were long and difficult.
Despite taking that set, Haas knew his shoulder was not going to have the power needed to play at an optimum level to get him through the third set in which he fell behind 4-1.
"Unfortunately, the shoulder kind of left me a little bit after the second set and I just didn't have the power that I needed," Haas said.
Malisse, who reached the quarterfinals in Chennai last month, has won this tournament twice and has been in the final five times since 1999. The Belgian was only able to take advantage of two of 17 break points in the match.
Reynolds, who won his first ATP match of the year with the victory over Malisse, converted four of his eight break-point chances.
"I tried to battle but I didn't have much confidence," Malisse said. "The wind made it even tougher. I played bad and made some bad decisions on the court. I don't mind losing if I'm playing well."