Roger Federer already has dropped two more sets at the U.S. Open than he did during his entire two weeks en route to the title at Wimbledon.
Worried about a recent back problem, Federer was a step or two off with his footwork at the outset. His backhand, in particular, was problematic. He had to overcome an early deficit and a late lapse Tuesday night to edge 19-year-old American Frances Tiafoe 4-6, 6-2, 6-1, 1-6, 6-4 in a compelling first-round contest under the Arthur Ashe Stadium roof.
"I had a bit of a slow start today, but Frances also felt good from the beginning. I was maybe a bit worried at the beginning with my back issue from a couple of weeks ago," Federer acknowledged, "but was eventually able to let go."
The No. 3-seeded Federer, whose most recent of five championships at Flushing Meadows came in 2008, got broken in the first game and dropped the opening set of the topsy-turvy match. He then appeared to take control by grabbing eight of nine games to seize the second and third sets. But he let that lead slip away. There was more trouble when Federer served for the match leading 5-3 in the fifth and got broken.
"He won by the skin of his teeth," Tiafoe said.
Federer's initial match point came at 5-3, 40-30 in that game, but Tiafoe staved that off, then broke. He produced a cross-court forehand winner at an unbelievable angle to earn the chance, before converting it with a terrific forehand passing winner down the line. Tiafoe roared and pumped a fist and sprinted to the sideline for the changeover.
When he had to come back out and serve, Tiafoe was a bit flat. Federer wasted his second match point with a netted backhand. On the third — with Federer's wife, Mirka, covering her eyes in the stands - Tiafoe hit a stumbling forehand into the net.
"In the fifth, it's a coin toss. It went my way tonight," Federer said. "To get through a five-setter, you have to be OK, somehow. So I believe this is going to give me great confidence in the body and also in my game."
It was Federer's 79th career victory at the U.S. Open, equaling Andre Agassi for second-most. Only Jimmy Connors has more, with 98.
Federer played with the roof shut at Ashe for the first time. He missed last year's tournament, when the retractable cover made its debut, because he took off the second half of 2016 to let his surgically repaired left knee and a bad back fully heal.
In 2017, he is 36-3 with five titles, including the Australian Open and Wimbledon, where Federer won every set he played across seven matches while collecting his record eighth trophy at the All England Club and 19th Grand Slam championship overall.
For more than a half-hour Tuesday, it appeared as if Federer was still dealing with the after-effects of having tweaked his back during a loss in the hard-court final at Montreal this month. He sat out the following week's tournament at Cincinnati.
Of the first 20 points won by Tiafoe, only two came via his own winners, a pair of aces. The rest were a result of Federer's miscues - 12 unforced, six forced - and Tiafoe gladly accepted the first set.
Tiafoe, who is from Maryland and now is based in Florida, is ranked 70th and has never been past the second round at a major tournament.
This was his second match against Federer. Tiafoe pushed Federer to a first-set tiebreaker when they faced each other in March at the Miami Masters before losing in two sets.
"Eventually," Tiafoe said, "I'll win more than I lose these."