The 39-year-old Englishman, one of Ian Woosnam’s assistants in last September’s victory over the Americans at the K Club, lost his European Tour card three years ago and relies mostly on invitations for the chance to play now.
This was Baker’s first start of the season and he built on two opening birdies by picking up further strokes on the fifth, sixth, 12th and 15th before dropping a shot at the short 17th.
He was in joint second place with US Tour winner Notah Begay, one behind Portugal’s Ricardo Santos.
One of Britain’s most promising players when he turned professional in 1986, Baker was in just his second full season when he beat Nick Faldo in a play-off for the Benson and Hedges International at Fulford.
His Ryder Cup cap came at The Belfry in 1993 and he picked up three points out of four, two of them with Woosnam as his partner.
But he has not won a single event since and is without a top-10 finish for almost three years.
Santos, a 24-year-old who had a plus-five handicap as an amateur, was one over after four, but then birdied seven of the next 10 holes.
Begay, a close friend of Tiger Woods, came through the Tour qualifying school last November after losing his playing rights in the States. He did not drop a stroke in his 67.
Defending champion Jean Van de Velde and Scotland’s Paul Lawrie – paired together and the two central characters of the Open championship drama at Carnoustie in 1999 – dragged each other down – both coming in with 75s.
Twelve players had still to complete their first rounds when play was suspended because of the fading light and earlier hold-ups caused by low cloud.