Juan Martin del Potro had to fight off a strong challenge from Belgium's Xavier Malisse before reaching the third round of the Queen's Club grass-court tournament with a 7-6 (5), 1-6, 7-5 victory on Tuesday.
The third-seeded Argentine had won just three matches in his previous two appearances at the pre-Wimbledon event and was playing his first tournament in more than a month since a respiratory illness kept him out of the French Open.
He edged the opening set but was then overwhelmed in the second and looked set for another early exit when he trailed by an early break in the third. But he rallied to level at 4-4 and then broke serve again at 6-5 to claim victory.
Earlier, Sam Querrey earned his 200th career singles victory by beating Aljaz Bedene of Slovenia 7-6 (11), 5-7, 7-6 (5) in a rain-interrupted match.
The sixth-seeded American saved a match point in the third set before winning the second-round contest, which endured four rain delays and took more than five hours to complete.
Bedene fell heavily while hitting a cross-court forehand winner to take the second-set tiebreaker. He was shaken up and received medical attention but was not injured.
With no breaks of serve in the final set, Querrey saved a match point at 6-5 before winning the deciding tiebreaker.
Among the seeded winners on Tuesday were France's Julien Benneteau and Lukas Rosol of the Czech Republic. But No.9 Benoit Paire of France was beaten 6-3, 6-4 by American Denis Kudla.
Three matches were postponed until Wednesday, including defending champion Marin Cilic against Ivan Dodig and Grigor Dimitrov against Lleyton Hewitt.