Former Ryder Cup star Thomas Pieters made an excellent start to his bid to win the D+D Real Czech Masters for the third time in eight years while Irish trio Cormac Sharvin, David Carey and Gavin Moynihan are seven shots off top after the first round.
Pieters won his first DP World Tour title at Albatross Golf Resort in 2015 and was runner-up 12 months later, before winning the event for a second time in 2019.
The 30-year-old Belgian was unable to attempt a second title defence in 2020 as the tournament was cancelled due to the Covid-19 pandemic, but carried on where he left off on Thursday with an opening 65.
Pieters birdied his first three holes and picked up further shots on the sixth and eighth to be out in 31, before responding to a bogey on the 10th with four straight birdies from the 12th.
The world number 35 will have been annoyed to find water off the tee on the 18th, despite taking an iron for safety, but ended the day just a shot behind South Africa's Louis de Jager, who compiled a flawless 64.
"I made some putts that me and my playing partners thought were going to miss today, the greens were getting very bumpy near the end," said Pieters, who won a record four points on his Ryder Cup debut in 2016.
"I think I got a bit of luck and I feel comfortable on the course. I hit driver everywhere, it seems crazy to think some people are hitting three woods or rescues off the tee.
"I'm thinking 'What are you doing?'. I just feel comfortable, I'll keep doing it and it works."
Pieters looked set to hold the clubhouse lead until De Jager, in the penultimate group, birdied two of his last four holes to edge in front.
Seven shots back sits the Irish trio of Sharvin, Carey and Moynihan who all posted first-round 71s to sit on one-under-par.
It was a tough day's work for Paul Dunne who carded 16 pars but still finished on four-over after bogeys at the fourth and eighth and a double bogey at the par-four 14th.
Michael Young retired after 16 holes of his round, he was seven-over-par at that point.
Defending champion Johannes Veerman carded a 66 to share third place alongside Marcel Schneider, Tapio Pulkkanen and American Jordan Gumberg, who shares the lowest possible world ranking of 1,965.