Luke Donald's quest to regain the World Number One position got off to a challenging start at the Zurich Classic.
Donald needs to finish in the top seven at the event in Avondale, Louisiana, if he is to reclaim top spot from Rory McIlroy - who does not return to action until next week's Wells Fargo Championship.
However, Donald could only manage an opening round of 73 - and at one over par the 34 year old sits eight shots off the pace set by Ken Duke and Cameron Tringale.
Three birdies and three bogeys were followed by a five at the par three 17th for Donald - although the Englishman got a shot back on the 18th.
Bubba Watson is also well off the pace after making his return to action following victory in The Masters Tournament.
Watson won this event last year but this time around he carded a steady opening round of 71, one under par.
The American had birdies on the second, sixth and seventh holes but bogeys on the eighth, tenth and 16th meant he needed a birdie on the 18th to finish the first round under par.
Duke had seven birdies in a bogey-free round, while Tringale - who is also seeking his first win on the US PGA Tour - recovered well after a bogey on the third, finishing with four birdies.
South Africa's Ernie Els, Sweden's Daniel Chopra and United States duo Steve Stricker and Chris Stroud are a shot behind the leaders on six under, with fellow Americans Ben Curtis, John Rollins and Jason Dufner on five under.
Northern Ireland's Graeme McDowell is the next-best European Tour Member after Els after the first round, on three under par.
