British prodigy Tom Lewis defied illness to card a level-par first round of 71 at the Castello Masters in Spain.
The 20-year-old, who in only his third event as a professional, was three over but carded four successive birdies.
"The head is really spinning, especially when I bend down, and I've got quite a temperature; it really affected my concentration," he said.
Ross McGowan, without a top-15 finish this year, leads by two at seven under.
McGowan, who has dropped from 63rd in the world rankings to 543rd, led the Madrid Masters a fortnight ago after another opening round of 64, before eventually finishing 42nd.
In Castello, seeking to move up from 163rd on the money list and secure his Tour card for next year, the 29-year-old posted five birdies and eagled the 503-yard par four 17th after holing his second shot with a four-iron.
Lewis, who recorded five birdies in his final seven holes to secure his maiden title last weekend, admitted this week's course, the Club de Campo del Mediterraneo, was not as well-suited to his game.
"It's going to be difficult for me this week," he said. "It's not just the head, the course isn't really set up for me. It's very tricky and narrow, not like last week at Victoria where the fairways are wider and the greens bigger.
"You need a good short game and my short game isn't my strongest point."
Local hero Sergio Garcia, a promoter for the event, played alongside Lewis and was one over after his first 10 holes.
However, the 31-year-old world number 49, without a win for almost three years, made five birdies in his closing eight holes to return a four under 67 for a share of fourth.
The third member of the group, defending champion Matteo Manassero, began with four successive birdies but also had a double bogey and the 18-year-old finished at two under.
Former Ryder Cup captain Colin Montgomerie had a steady round with 17 pars and one birdie, while colourful American John Daly finished with consecutive double bogeys in his 73.