Former Open Champion Louis Oosthuizen and England's Brian Davis shared the lead on 11 under at the end of day two of the Shell Houston Open.
But with 70 players, including America's Jeff Maggert who was a shot behind, yet to finish their second rounds because of bad weather on day one, their position was anything but secure.
Davis produced a blemish-free seven under round of 65 to take his place at the top of the leaderboard.
And he was joined their by South African Oosthuizen, who also went round without dropping a shot in his six under 66.
But Maggert was four under through ten for a ten under total when the players were forced off by bad light, and just a shot further back was another American, James Driscoll, who was four under having played just seven.
Driscoll was in a group of five players on nine under which also contained England's Greg Owen and America's Phil Mickelson.
Thursday's rain had cleared by the time play got under way on Friday, but because of damp fairways the players were allowed to lift, clean and place their balls in the fairways.
"It was a good day at the office today," Davis, who has never won on the US PGA Tour said.
"It was tougher this morning because we didn't have ball in hand to start the round and we had the rain yesterday.
"This morning was pretty tough. The ball was flying everywhere. We got the ball in hand this afternoon, you know, [and] got a flag to go at."
Mickelson, meanwhile, was pleased with his position heading into the weekend.
"I played really well," he said. "I didn't quite take advantage of the opportunities that I did in the [first] round where I hit a lot of good shots close. Ten, 12, 15-footers I made in the first round, I caught lips in the second.
"There was a lot of good things to build on heading into the weekend. I feel really good about where my game is at. I'll be able to shoot a little bit lower score than I did this afternoon."