Drysdale needed a special invite to take part in the tournament
FIRST ROUND LEADERBOARD:
-6 J Edfors (Swe), D Drysdale (Sco)
-5 Darren Clarke (NI), Miles Tunnicliff (Eng)
-4 J M Olazabal (Spa), A Butterfield (Eng), D Bransdon (Aus), Raymond Russell (Sco)
Scot David Drysdale and Sweden's Johan Edfors shared the lead after round one of the Scottish Open at Loch Lomond.
Both players carded six-under-par 65s to sit on top of the leaderboard, one shot ahead of Northern Ireland's Darren Clarke and England's Miles Tunnicliff.
Edfors is enjoying a successful season after wins in the TCL Classic in China and the British Masters at The Belfry.
American veteran Hale Irwin, 61, is also in contention after a surperb 68 left him three shots off the lead.
Irwin's performance impressed playing partner Edfors, who recorded four birdies in the first five holes
"I don't think I've ever seen a better display with long irons and fairway woods," said the 30-year-old Swede, who added another five birdies but also carded three bogeys.
There's such a long way to go - it's a good start, but anything can happen
"He's getting shorter off the tee, but every shot was straight at the flag. It was pretty impressive - amazing."
Irwin won the first of his three US Opens way back in 1974 before Edfors was even born and captured the last of them in 1990 when he was 45.
He remains the oldest winner of that trophy and since then has earned a record £16m in seniors golf.
Drysdale, who is not even on the European Tour and is ranked 293rd in the world, carded a bogey-free round.
"I thought I'd be sticking to the Challenge Tour, so to get in here is a big bonus," said the 31-year-old from Dunbar, who received a special invite to play.
"Now to be leading is fantastic - I am over the moon. I'll just try to take one shot at a time. There's such a long way to go - it's a good start, but anything can happen."
Couples will now focus on being fit for the Open at Hoylake
Luke Donald is alongside Irwin on 68, while David Howell, Lee Westwood, Tom Lehman and defending champion Tim Clark shot 69s.
Ernie Els and Retief Goosen, who have also won the event, are one under.
Fred Couples pulled out of the event before hitting a shot because of a back injury.
He had withdrawn from Wednesday' pro-am event as a precaution but decided he was not fit enough to start.
"I couldn't have even walked down the first fairway, let alone play," said the 46-year-old American.