Federer was denied a record-extending seventh title when he was felled by a resilient Djokovic 7-6 (6), 7-5 in a gripping contest in London, giving the world No. 1 a second triumph at the elite eight-man event and a sizable lift heading into 2013. Federer will rue not maintaining leads in both sets.
"You have to get over the finish line in the set and then obviously in the match," Federer said. "He was better at that today."
Early Federer dominance: Don't you love those quick Federer starts?
He needed a mere 50 seconds to take a 1-0 lead, holding to love. He won the opening nine points, in fact, as Djokovic looked slow and sluggish.
Somehow, Djokovic broke back for 2-3. The set then truly began. And what a set it turned into.
"It's not the first time that Roger starts against me so well," said Djokovic, who dedicated the win to his father, in intensive care in hospital with an undisclosed illness. "I've experienced before his [aggressiveness], really trying to put his mark on the match. It's what he's done again.
"You know, I didn't know in which direction the match would really go, but I tried to convince myself that I will make a turnaround."
The turnarounds: When Djokovic hunched over after missing a forehand down the line at 3-4, you expected Federer to take advantage and re-establish his break advantage. It never did happen.
At 4-4, Djokovic broke -- helped by a stunning off-balance forehand pass. With six deuces, the game had the feel of a momentum-changer.
But cruising at 30-0 and trying to serve out the first, Djokovic unraveled. He went on to make five unforced errors, including one on set point, as Federer leveled proceedings at 5-5.
In trouble at 5-6, 0-30, Djokovic's serve carried him to a tiebreaker.
A classic tiebreaker: They split the first six points for 3-3, which was about right since both missed comfortable forehands when in control of two different rallies.
Federer engineered a shot only he could, really, to fend off a second set point at 5-6. For a start, not many players would have been able to track down and execute a lunging forehand volley.
Djokovic, initially slow to react because he suspected the ball wasn't coming back, raced up to retrieve the drop and steered it down the line, behind the Swiss. No problem: Federer swiveled and ripped a forehand cross court. He let out a loud roar -- only to lose the ensuing two points.
Seventy-two minutes of theatre produced for London's West End.
A new set: So, this was now Djokovic's match, right?
Federer wasn't cooperating.
The first game of the second set lasted 11 minutes, and Federer converted on his fourth break point to seize the initiative. Djokovic managed to avert trailing by two breaks and worked a break point of his own at 3-4. Federer saved it with an ace, and Djokovic gave Federer a freebie at deuce when his sitter of a forehand went wide.
Almost game, set and match: We all began to settle in for a third set when Federer held set points serving at 5-4, 40-15. How foolish of us.
If Djokovic could save match points in back-to-back U.S. Open semifinals against Federer, what are two set points here? Djokovic disappointed the locals by breaking for 5-5, and that was almost that.
Just for good measure, he came back from 30-15 on the Federer serve at 6-5, sealing the riveting encounter with a sparkling backhand down the line.
The chocolates were needed: Djokovic won over journalists Sunday when he handed out chocolates in his postmatch press conference. It was a way of saying thank you for their "cooperation" in 2012. No, he didn't steal a few Lindts from Federer.
Djokovic should have given chocolates to the fans at the O2 Arena on Monday evening -- more of them would have rooted for the Serb. Federer was the firm favorite, and when he lost the first set, more so.
When will spectators back Djokovic?
They love his impersonations and humor, but whenever Djokovic meets a fellow member of the big four -- or anyone? -- the crowd invariably supports his opponent.
By the numbers: Likely a combination of less juice on the serve and fine returning, Federer and Djokovic's percentages won behind the first serve didn't surpass their first-serve percentages. Sound confusing? This should clear it up.
Federer served at 62 percent and won only 62 percent of those points; Djokovic served at 69 percent and won 63 percent of those points.
Another notable statistic: Federer committed 24 forehand unforced errors; he totaled eight forehand winners.
"Sometimes I wish I wouldn't have missed and I'm surprised I missed," Federer said. "But then again, it's all a matter of how the ball gets to you, what has happened in the last five minutes, two minutes, 30 minutes. You just have to absorb all of that, compress it into that one decision you have to make when the ball comes to you.
"Sometimes you think there is a gap, there is not a gap, then you push and miss it by a little bit. Yeah, I mean, I think with all those errors, I still played a good match."
Adios, Lars: What a way to go out, officiating a Federer-Djokovic match.
Lars Graff was in the chair for the final time before retiring, and Djokovic gave the Swede a pat on the back following the coin toss.
Graff must like London. He was in charge of the 2009 Wimbledon final between Federer and Andy Roddick -- the one that ended with a 16-14 fifth-set win for Federer.
Star struck: Among those in attendance was Pippa Middleton, sister of the classy Duchess of Cambridge.
We ask: Is showing up at major sporting events in the UK Middleton's full-time job?