NORTON, September 1, 2014 (AFP) - The 25-year-old McIlroy stormed up the leaderboard with a seven-under 64 on Sunday to move into contention at the TPC Boston.
"I am happy to have another chance for a win here in Boston," McIlroy said.
"I have good memories from 2012 when I chased down the lead ... Need to do the same tomorrow."
McIlroy, the 2012 Deutsche Bank winner, vaulted into a share of third place with the day's best round to reach 10-under-par 203, two shots adrift of Henley.
After an up and down opening two rounds, McIlroy needed just 27 putts on Sunday.
"I don't think you ever (know a good round is coming)," he said. "You just keep playing and take it one hole at a time. The first couple of days I played well at the start, just couldn't keep it going."
McIlroy, from Northern Ireland, could return to the top of the FedEx Cup standings with a solid Monday finish after having his three tournament win streak snapped at the Barclays event last week.
Henley, 25, ended three rounds at 12-under-par 201. He will go for his third USPGA Tour title on Monday.
Billy Horschel posted a four-under 67 to move into second place at 11-under. Chris Kirk, who was paired with McIlroy, also fired a 64 to jump into a share of third place at 10-under-par. McIlroy and Kirk were joined there by second-round co-leader Jason Day (69).
Henley beat McIlroy earlier this year in a playoff to win The Honda Classic. His 65 Sunday was one of six scores 65 or better in the third round.
"Nobody is really expecting me to be sitting here right now," Henley said. "And that is kind of how I like it."
Former tournament winner Webb Simpson moved into sixth place at nine-under behind a third-round 68.
Ryan Palmer, who shared the second-round lead with Day, posted his second straight 71 on Sunday. He dropped into a tie for seventh at eight-under 205.
Palmer was joined there by Kevin Streelman (65), South Korea's Noh Seung-Yul (68) and American Keegan Bradley (69).
Leading scores on Sunday from the third round of the USPGA Tour's Deutsche Bank Championship (par-71, USA unless noted):
201 - Russell Henley 70-66-65
202 - Billy Horschel 69-66-67
203 - Jason Day (AUS) 66-68-69, Rory McIlroy (NIR) 70-69-64, Chris Kirk 73-66-64
204 - Webb Simpson 66-70-68
205 - Ryan Palmer 63-71-71, Kevin Streelman 73-67-65, Seung-Yul Noh (KOR) 69-68-68, Keegan Bradley 65-71-69
206 - Geoff Ogilvy (AUS) 70-71-65, Bill Haas 67-69-70, Rickie Fowler 70-69-67, Jordan Spieth 67-70-69, Chesson Hadley 66-73-67
207 - Jim Furyk 72-66-69, Ben Crane 69-68-70, John Senden (AUS) 69-71-67, Martin Kaymer (GER) 71-66-70, Robert Streb -6 (73-67-67=207)