Graeme McDowell was four shots off the pace at the Masters as he carded a battling opening level-par 72 on a tricky day for scoring at Augusta.
The 2010 US Open champion parred his opening nine holes before bogeys on 10 and 11 left him on two over.
However, the Portrush man birdied the par-five 13th and a further gain at the 17th saw him signing for a 72.
2011 Open champion Darren Clarke also battled well to card a 74 while Bill Haas was the clubhouse leader on 68.
Clarke, 45, dropped a stroke at the first and went to the turn in three over after further bogeys at the fifth and seventh.
A rare birdie at the tough 10th saw the Dungannon man improve his position to two over but he followed that with immediately bogeys at the 11th and 12th.
However, Clarke managed birdie fours at the 13th and 15th to get back to two over before parring his closing three holes.
Former Tour Championship winner Haas was two under at the turn and birdies at the 13th and 14th moved the American to four under.
Haas, 31, dropped a stroke at the 17th but a tremendous approach to the last to three feet yielded another birdie.
Defending champion Adam Scott and Louis Oosthuizen finished on 69 while American quartet Brandt Snedeker, Jimmy Walker, Kevin Stadler and Gary Woodland were in the clubhouse on two under along with Sweden's Jonas Blixt and Korea's KJ Choi.