(CNN) -- Steve Stricker shares the lead at the Deutsche Bank Championship with South Africa's Retief Goosen and fellow American Sean O'Hair, but Tiger Woods is nine shots back after the third round.
Stricker celebrates his crucial eagle on the 18th to give him a share of the lead.
Stricker would take the lead from Woods in the FedEx Cup standings if he wins in Boston on Monday, powering into contention after a six-under 65.
The trio are on 13-under 200 with Goosen, bidding for his second win of the season, shooting a three-under 68 and O'Hair carding a 70.
Woods, troubled by poor putting again, toiled to a one-over 72, hitting his tee shot into the tees on his first hole.
But Stricker will have to battle hard for victory on the final day with a congested leaderboard behind the leading trio.
Three-time major winner Padraig Harrington mounted his challenge on Sunday, carding a four-under 67, urged on by thousands of Irish supporters on the course.
He is in a three-way tie at 12-under 201 with Kevin Na (66) and Scott Verplank (68).
Americans Jerry Kelly (67) and Kevin Sutherland (69) are two shots back of the leaders at 11-under 202.
Stricker claimed his share of the lead with an eagle on the 18th hole to go with seven birdies, recovering superbly after a poor second round.
"I was disappointed after yesterday's round, very disappointed," he told www.pgatour.com.
"The emphasis today was grind a little bit harder on my putting and concentrate a little bit harder on my putting and make some good strokes, and I did today, which was very satisfying."
Jim Furyk, who shared the joint overnight lead, slipped down the field to 10-under after a two-over 73, but two late birdies gave him hope for the final day.