Todd has a two-stroke lead midway through the World Golf Championships event.
Brendon Todd watches his tee shot on the 18th hole during Saturday's third round of the World Golf Championship-FedEx St. Jude Invitational in Memphis, Tenn.
But in typical fashion, defending champion Koepka made six birdies from the ninth to the 16th hole.
Scores of 64 and 65 over the first two rounds saw Todd lead the way by two shots at the halfway stage but a mixed one-under 69 on Saturday left him at 12 under for the tournament and allowed the chasing pack to close in.
McIlroy required 16 holes to discover a birdie on Thursday, however he delighted in an even more uplifting start to his 2nd round as he birdied the 3rd, 4th and 5th, and another at the 10 th transported him into red numbers prior to a scrappy 13 th hole cost him his only bogey of the day.More news: South Africa: Cases of COVID-19 top 500,000
Fourth-ranked Webb Simpson, another two-time victor this season, totaled 66 with four birdies on the back nine and is six strokes down in a tie for eighth with Jason Day of Australia, who had a 67, Louis Oosthuizen of South Africa, who also shot 67, and Sungjae Im of South Korea, who came in at 68.
Mickelson is seven under alongside Chez Reavie (70), Louis Oosthuizen (68) and Englishman Matt Fitzpatrick, who salvaged a 69 thanks to a hat-trick of birdies from the 14th. He won on this course in 2018 before the event became a World Golf Championship in 2019.
On Friday, his putter worked well enough that he needed only 24 putts in a round that featured a 50-footer for birdie on the par-3 No. 14.
Fowler holed out from the green-side rough on the par-5 third to pull within two.More news: Apple Watch Series 6 to Feature Blood Oxygen Monitoring
Todd took the lead back to himself on the next hole with a 22-foot birdie putt on the par-3 eighth. He also sank a clutch 10-foot par putt at the 18th. "It happened to just drift right there in the middle of the hole".
Fowler then ended up in design with another not likely birdie from outdoors 40 feet, and he stated: "It's been good to see some putts enter, and these greens have to do with as excellent as they get".
Rickie Fowler (69) ended the day two back from the lead after a pair of bogeys on the back nine dented an otherwise clean round.
A bogey dropped him to 12 under.
"'Frustrated' is not the right word because I understood the severity of the pandemic and we do what we had to do in taking a break from golf", Todd said of the PGA Tour shutdown because of the Coronavirus pandemic in March when he was on top of his game. "It was a swing that was out of rhythm that was a little bit too often today and to know I hit the water there, it made me pretty mad". "There were a couple of pins I think that were more hard on one, 14 and 16, so there were some birdie opportunities, but you still have to place the ball in the right area and make some putts".More news: Lizzo Throws Ultimate Vegan Watch Party for Beyoncé's Black Is King Premiere
"I would say I'm probably more excited and happy about the resumption of play and being able to complete this season". He finished with a 71, his first time over par at this course in seven rounds.