(AFP) - Bill Haas was sitting tight atop the leaderboard as he teed off in the second round of the Masters on Friday.

The 31-year-old American carded a four-under 68 on Thursday and he had the luxury of being able to sit back and see who could challenge him early on at Augusta National.

Several players tried and at one stage Australian Marc Leishman overhauled him at five under, but he promptly bogeyed the next two holes.

Major winners Bubba Watson and Louis Oosthuizen both managed to draw level with Haas, but then both dropped strokes to fall back, the South African with a triple bogey eight at the 15th.

Watson, though, came back again to get to four under through 12 holes with Kevin Stadler joining him and Haas at four under through seven.

Much of the day's focus was on the late groupings, starting with Haas.

Defending champion Adam Scott, also one stroke back from the overnight lead, was in the penultimate grouping at 1748 GMT with Rory McIlroy (71) the last man to tee-off in the company of Jordan Spieth (71) and Patrick Reed (73).