|Celtic Classic first-round leaderboard|
|-7 T Pieters (Bel); -6 J McLeod (Aus), T Tree; -5 S Kim (Kor), M Warren (Sco), S Soderberg (Swe), A Meronk (Pol), G Migliozzi (Ita), N Elvira (Spa), E Molinari (Ita)|
|Selected others: -2 R Enoch (Wal); -1 O Fisher (Eng), C Hill (Eng), J Donaldson (Wal)|
Thomas Pieters returned from five months away from competitive golf to lead the Celtic Classic by one shot after the first round at Celtic Manor.
The Belgian, 28, came home in 29 shots in a seven-under 64 on a day when play in the European Tour event was put in the shade by positive Covid-19 tests.
Frenchmen Alex Levy and Romain Wattel are out of the event after the former tested positive for coronavirus.
Levy, 30, initially returned a negative test, but a retest came back positive.
Wattel and Levy's caddie, Tom Ayling, have so far tested negative but all three men are self-isolating.
Pieters had not played since March after delaying his return to competitive action following the birth of his first child during the coronavirus shutdown.
But the 2016 Ryder Cup player's round on the Twenty Ten course gave him a one-stroke advantage over Toby Tree and Jake McLeod.
Pieters impressed on his Ryder Cup debut - forging a fine partnership with Rory McIlroy and setting a new rookie record for points earned - but has struggled to hit those heights in the past three seasons.
"It was pretty good. I putted well and kept my ball in play, so I didn't really get myself in trouble," Pieters said.
"It has been fantastic. I miss my little baby girl, but I am thankful I can play golf right now. It is the first event in five months, so it feels nice to get out there and actually put a score down."
Italian Edoardo Molinari, who was part of Europe's Ryder Cup-winning team at the Newport venue a decade ago, is a further shot behind on five under alongside six other players including Scotland's Marc Warren.
Welshman Rhys Enoch is two under and compatriot Jamie Donaldson is one under.