VILAMOURA, October 9, 2014 (AFP) - No-one in the Tour's 42-year history has ever dipped below 60 but the 31-year-old former Ryder Cup player was within a hairsbreadth at the Oceanico Victoria Golf Club.
His 20-foot birdie putt just missed the lip of the 18th as he fell short by just a single stroke.
Colsaerts had carded seven birdies and then two sensational eagles at the 15th and 17th to set up the chance for a historic putt.
He drove straight down the middle of the fairway at the last and that was followed by a short iron for what appeared to be a makeable putt.
But he just missed and had to settle for a 60 -- the 19th time the score has been managed on the European Tour -- and a three-shot first round lead.
"When I made eagle on 15, I knew then that if I birdied the last three, that would have been 59," Colsaerts said.
"I hit a good drive (at the last). It's too bad it (the putt) just shaved the edge.
"I thought it was going to be slightly left to right at the end and it kind of went straight and basically just left it hanging. Too bad, I thought it was a pretty good effort."
Colsaerts completed his round shortly before play was abandoned when a torrential downpour flooded large parts of the course.
His closest challengers were Scotland's Scott Jamieson and Frenchman Alexander Levy, who both carded eight-under-par 63s.
Oliver Wilson, who won the Dunhill Links Championship in Scotland last weekend, shot a one-over-par 72 while Paul McGinley, Europe's victorious Ryder Cup captain, hit a four-under-par 67.
Leading first round scores in the Portugal Masters at Oceanico Victoria Clube de Golfe on Thursday (first round to be completed Friday morning after heavy rain caused play to be abandoned; GBR/IRL unless stated, par 71):
60 - Nicolas Colsaerts (BEL)
63 - Alexander Levy (FRA), Scott Jamieson
64 - Rafael Cabrera Bello (ESP)
65 - Felipe Aguilar (CHI), Danny Willett, David Lynn, Christopher Doak
66 - Richard Bland, Thomas Aiken (RSA), Jbe Kruger (RSA), Branden Grace (RSA), Eduardo De La Riva (ESP)
67 - Emiliano Grillo (ARG), Ross Fisher, John Hahn (USA), Paul McGinley, Nacho Elvira (ESP), Thongchai Jaidee (THA)
68 - Lucas Bjerregaard (DEN), Chris Wood, David Drysdale, Roope Kakko (FIN), Daniel Brooks, Julien Quesne (FRA), Pablo Larrazabal (ESP)
69 - Magnus A Carlsson (SWE), David Horsey, Gary Stal (FRA), Darren Fichardt (RSA), Alvaro Quiros (ESP), Ricardo Gonzalez (ARG), Peter Uihlein (USA), Marc Warren