Lleyton Hewitt and Tommy Haas struggled to overcome dogged opponents before reaching the second round of the Thailand Open on Wednesday.
Second seed Hewitt, playing his first match since losing to Roger Federer in the semi-finals of the U.S. Open, survived an enterprising challenge from Czech Lukas Dlouhy to win 6-3, 3-6, 7-5.
Haas, just days after winning the deciding rubber in Germany's Davis Cup victory over the Czech Republic, edged past 147th-ranked Irakli Labadze 6-3, 4-6, 6-4.
Australian Hewitt appeared set for a runaway victory as he swept to a 4-1 lead, but once Dlouhy settled he offered a real challenge.
His adventurous play paid off as he tormented Hewitt with his strong serve, which he often followed up with a clean volley and a willingness to chase down every ball and produce winners from difficult angles.
Hewitt struggled to find consistency, and the match remained evenly balanced until Dlouhy finally conceded with a double-fault.
Haas said that he was not at his best against Labadze, suffering with an injury that was treated at the end of the second set, and with jet-lag.
"To be honest, I didn't feel one 100 percent out there today. My left hamstring is pretty tight," said the German.
"He (Labadze) doesn't give you much rhythm, and I didn't have the greatest preparation. I came in yesterday afternoon and had only one hit and slept only four or five hours last night."
Fourth seed Haas was never able to stamp his authority on his Georgian opponent, who struck some stinging returns, served well and showed some fine touches at the net. Haas also served well and fired 10 aces, but he showed only a few glimpses of his blistering backhand.
Labadze held off two break points at 1-0 and then broke to lead 2-1, but Haas settled and claimed five straight games to take the opening set.
Haas also held the edge in the second set, failing to break for 1-0 but then breaking in the fifth game and holding for a 4-2 lead.
But Labadze levelled at 4-4, and then produced the finest shot of the match, hitting a ball on the run that swept round the post and landed in the corner to give him the second set.
Haas also held the advantage in the final set. He was solid on his serve, surrendering just three points in the set, and he finally produced a tremendous backhand when it mattered most, hitting a winner down the line to break for 5-4.