It was a good day for two of the Irish stars too, with Des Smith firing a 66 to share second place, two behind leader Fred Funk.
Cork’s Denis O’Sullivan is also well in contention after an impressive 68.
Watson, however, was the star attraction. The 59-year-old American, who came agonisingly close to becoming the oldest major winner in history before missing out to Stewart Cink last weekend, insisted it was not difficult to put that disappointment behind him after his three-under-par round at Sunningdale.
“That was a big story last week for me,” said Watson, who is looking to win this title for the fourth time. But here it’s a different story this week. I’ve got to write it – let’s get on with it.”
Watson showed no sign of the putting nerves that appeared to get the better of him on the final hole at Turnberry over the opening holes yesterday, draining birdie putts on the first, fourth and fifth holes.
At the par-three 13th Watson missed a birdie effort from eight feet – the same distance as his missed putt at the last in Scotland which would have given him a sixth Open title.
“I’m not very good at eight-footers right now,” he joked.
On the 18th his birdie effort lipped out to leave Watson three shots behind compatriot Fred Funk, who posted the lowest opening round in a Senior Open Championship with a 64.
Funk was only one under par at the turn thanks to a birdie at the par-five opening hole, but the 53-year-old burst into life on the back nine with five birdies, including one at 17 where he chipped in from a bunker.
Funk’s round gave him a two-shot cushion over compatriots Jay Haas and Loren Roberts, Ireland’s Smyth and South African Chris Williams.
Meanwhile Henrik Stenson’s hopes of donating the first prize of nearly €166,000 to his own charitable Foundation took a blow yesterday when he began the SAS Masters in Malmo with only a level par 73.
At 7,665 yards Barseback, Stenson’s home course, is the longest in European Tour history.
The world number seven thought that would be in his favour, but he trails England’s Lee Slattery by six — and was relieved it was not by more.
“I played like a pig and got away with murder,” said Stenson. “I didn’t play well at all, but the little Seve and Houdini in me was out there.”
Stenson was again wearing a green ribbon in support of an Iranian friend, as he did at The Open last week.
“It’s a symbol for democracy in Iran and I felt it was an important gesture.”
Slattery, ranked 497 places below Stenson, holds a one-stroke lead over Argentina’s Ricardo Gonzalez.
Ireland’s Gary Murphy is tied 12th after a two-under 71. Gareth Maybin and Michael Hoey are both one under. Peter Lawrie and Damien McGrane both fired par 73s.