British number one Cameron Norrie shook off illness and an early setback to beat South Korean Kwon Soon-woo to reach the Madrid Open second round.
Norrie, 26, was broken in his opening service game and trailed 4-1 in the first set, saving two set points before winning 7-5 7-5 against the qualifier.
"I've been a little bit sick, I sound like I've just smoked a packet of ciggies," said Norrie, who faces American John Isner next.
"But I'm feeling better every day."
He told Amazon Prime: "I was happy to even play here this week and was just fortunate to get a win like this against Soon-woo, who was confident and playing well."
Wildcard Andy Murray, a two-time champion here, starts his campaign later on Monday against Austria's Dominic Thiem, who is returning from a wrist injury.
In the day's other action, Italian 10th seed Jannik Sinner saved three match points in a 6-7 (4-7) 7-6 (7-4) 6-3 victory over American Tommy Paul.
Meanwhile, in the women's event, Romanian former world number one Simona Halep reached the quarter-finals with a 6-4 6-4 win over American 18-year-old Coco Gauff.
Halep, the 2018 French Open champion who is unseeded in Madrid following a series of injuries, has yet to drop a set as she finds some good form before the clay-court Grand Slam at Roland Garros later this month.