(CNN) -- Luke Donald faltered in his bid to top the money list on both the European and PGA Tours after a one-under-par 71 left him five shots off the pace at the halfway stage of the Children's Miracle Network Hospitals Classic in Florida.
England's Donald needs to finish in at least a share for second at the final PGA Tour event of the season to overtake Webb Simpson in the U.S. money race.
But he trailed the trio of Justin Leonard, Swede Henrik Stenson and South Korean Bi-o Kim, who were on 12-under 132 at the Disney World resort.
Simpson, who has partnered Donald for the first two rounds, was also on seven-under-par after a three-under 69 on the Magnolia Course, one of two being used for the event.
Donald, trying to become the first golfer to win the European and PGA money titles in the same year, was not happy with his performance.
"It was very ugly. It wasn't very good at all," Donald told the official PGA Tour website.
"Obviously, it's not the hardest course in the world, but I didn't do many things well."
The World No.1 comfortably leads second-placed Rory McIlroy in the European Order of Merit by over $2.2 million but Simpson moved ahead of him by $363,029 last week.
They will be playing partners again Saturday for the third day in a row on the Palm course, but have ground to make up on the leaders.
If Donald takes the top prize of $846,000, Simpson would have to finish alone in second to deny Donald the title.
If Donald finishes in lone second, Simpson must finish no worse than alone in eighth place, to hold him off.
If Donald shares second for $413,600, Simpson needs at least a four-way share of 21st to keep grip of the coveted prize.
"I'm going to have to go pretty low on the weekend," admitted Donald, who opted to play in the tournament at the last minute..
"(Would) be nice to shoot a low one tomorrow, get in the mix, and make this one a bit fun for me and everyone else."