Andres Romero opened up a one-shot lead heading into the final round of the Omega European Masters but Ryder Cup stars Tommy Fleetwood and Rory McIlroy were well in contention in Switzerland.
Argentinian Romero's hopes looked to be fading when he dropped three shots in his opening five holes and McIlroy and Australian Wade Ormsby established a two-shot lead.
But as McIlroy and Ormsby produced late stumbles, Romero came home in 31 to sign for a 66 and lead the way at 14 under.
The 38-year-old produced a brilliant run of scoring on the back nine, going birdie-eagle-birdie-birdie from the 13th to edge a shot ahead of Ormsby, who bogeyed the last in his round of 67.
Englishman Fleetwood had bogeyed the second, third and sixth playing alongside Romero but birdied the ninth, 12th, 14th, 15th and 17th to sit at 12 under alongside Malaysia's Gavin Green.
"It's easy to get down on yourself," Fleetwood told europeantour.com. "It was a terrible start but I didn't do that much wrong.
"I had a good finish. It's that kind of golf course where you can get hot. Tomorrow I definitely need a better start but the back nine, need more of that."
World number two McIlroy arrived in Crans Montana just hours after lifting the FedEx Cup in Atlanta on the PGA Tour and showed signs of fatigue as he bogeyed three of his last five holes to sit three shots off the lead after a round of 69.
"I felt a little flat out there, a little tired," the Northern Irishman said. "Maybe it just all caught up with me. I'm looking forward to getting to bed early and getting a good night's sleep.
"I played pretty solid, made those mistakes coming in. If I go out and play a good front nine tomorrow I'll be right in it."
Christiaan Bezuidenhout, Lorenzo Gagli and Kalle Samooja were also at 11 under, a shot clear of major champion Sergio Garcia, Renato Paratore, Matthias Schwab and Sebastian Soderberg.