Tour rookie Shawn Stefani maintained his place at the head of the leaderboard on the second day of the Tampa Bay Championship.

The 31-year-old failed to scale the heights of his opening-round 65, settling for a more modest one-under 70 as he held on to the lead at seven under.

The American led by one stroke from Australia's Adam Scott, who followed up an opening 70 with a much-improved 66, and South Korean KJ Choi, who was four under for his second round.

Despite his drop in level - he carded three birdies against two bogeys - Stefani was satisfied with his round.

"Today was a little bit more of a struggle ball-striking," he told "I didn't really drive it super great, didn't hit some of the best iron shots.

"But I scrambled well and I putted really great. So you know, when you putt good, that usually keeps rounds going, and that was pretty much what happened today."

Stefani said nerves at his unaccustomed position at the head of the field was were not an issue.

"I wasn't any more nervous than I am any round," he said.

"I think I'm always a little bit excited about playing and I get a little nervous, which I enjoy."

Scott sank five birdies in a blemish-free round.

"I didn't really drive it super great, didn't hit some of the best iron shots" - Stefani on his round

"To go bogey-free anywhere is good," Scott said. "And I think [to do it] here is particularly good. It's quite a tricky golf course and mistakes are easily made."

Scott and Choi sat one stroke clear of a quartet of Americans tied for fourth place, Jason Dufner's 66 moving him into contention alongside Peter Tomasulo (68), Harris English (69) and Brian Harman (70).

Sergio Garcia followed his level-par first round with a 67 to lead the European charge on four under, while Brian Davis was the leading Briton on two under.

Defending champion Luke Donald was one over for the day to sit level overall, and Scotland's Martin Laird scraped into the weekend on two over, but Greg Owen, David Skinns and Ross Fisher missed the cut.