John Senden has slipped off the pace after a promising start in the opening round of the Arnold Palmer Invitational in Florida. The Australian began well with two birdies on the front nine but three costly bogeys down the back nine left him at even-par for the day, five shots adrift of the leaders Fred Couples and J.J Henry. Fellow Australian Matt Jones, who recently finished fourth at the Honda Classic, also had an inconsistent day carding four birdies and four bogeys to finish alongside Senden at even-par. 48-year-old Couples turned back the clock with a performance reminiscent of the 1990s, carding a five-under 65 to match Henry, one stroke ahead of Tom Lehman, Vijay Singh, Lee Westwood and Lucas Glover. “I feel like I can always hit the ball well,” said 1992 Masters champion Couples. “This guy said my swing may feel differently because a few of the things that he did would make the body work differently and, oddly enough, my swing feels different. “I don&apost know if it feels better or worse, but I&aposm able to slash through the ball, which two years ago I could do periodically.” A back problem restricted Couples to three tournaments last year, and he is playing this year as he stands inside top 25 all-time money winners. Henry made his move around the turn, picking up four birdies in an eight-hole stretch. “It&aposs been a little bit frustrating, the start of the year,” he said. “I&aposve worked really hard, felt I&aposve been close and for one reason or another had not quite figured it out. “Everything clicked and I hit a lot of fairways and greens, which you have to do on a difficult course like this. Obviously there&aposs a long way to go and I&aposm really excited the way I hit the ball.” Geoff Ogilvy, Stuart Appleby and Peter Lonard finished the day at two-over par while Nathan Green is a further shot behind at three-over the card. An out-of-sorts Tiger Woods hit some uncharacteristically poor short iron shots and managed just two birdies in a mediocre even-par 70 in benign morning conditions at Bay Hill. But as bad as it seemed, he still ended the day in the top third of the field, tied for 34th.