Swede Henrik Stenson set the pace at the BMW International Open in Munich with an eight-under-par 64.
The former Ryder Cup star had fallen from fourth in the world to outside the top 130 in two years but returned to form at last week's US Open.
England's Gary Boyd is one shot back on seven under while Scotland's Paul Lawrie is six under.
Sergio Garcia's recent encouraging form continued as the Spaniard carded a first-round 69.
Stenson, who finished tied for 23rd at the US Open after two years in the wilderness, fired an eagle and seven birdies on Thursday.
"I don't think you will find a player who's been out here 10 to 15 years who has not had some rough times," he said.
"We all go through ups and downs. I've been struggling with my game a little bit, but it's hard to put my finger on what it's been.
"I played a lot better last week. My confidence is still not as high as it can be, but I'm working away trying to do the things that are going to lead me back."