LONDON—When the first championship point for Novak Djokovic arrived less than 90 minutes into his match with Rafael Nadal, the response from the crowd at the O2 arena was muted and disbelieving. Could this 39th meeting between two titans of the modern game—one finishing one of the most remarkable seasons of his career, the other having found a rich vein of form that had seen him win 21 matches since the U.S. Open—really be over so quickly?

Not quite, as it turned out; but even Nadal could only postpone Djokovic’s victory for a brief time. He made a remarkable get to fight off the second championship point, but the Serb took the third, a 22nd straight victory, and a third ATP World Tour Finals title, 6-3 6-4.

We’re used to long, convoluted encounters, full of sudden reversals and defeat-defying recoveries from these two, but this was by and large a straightforward victory for Djokovic. Twice, it could have turned into a rout: Leading 3-0 in the first set and 4-2 in the second, Djokovic had points to turn a single-break lead into a double.

His failure to do so in the first set galvanized Nadal into momentarily wresting back the initiative from Djokovic, who had started the match looking infinitely sharper than the Spaniard. Djokovic won 11 of the first 14 points largely because of his down-the-line backhand, which he was striking beautifully at every opportunity—a helpful stat early in the second set showed that he was hitting 59 percent of backhands down the line, as opposed to 36 percent in earlier matches.

Having taken his foot off his opponent's neck with a couple of poor unforced errors in that 3-0 game, Djokovic played a poor service game himself to be broken back, and Nadal started producing some more proactive tennis to level the set at 3-3.

But again Djokovic’s backhand did the damage; he hit it flatter, harder, and caught Nadal on the hop by injecting cross-court pace. Two double faults from Nadal, pressured by Djokovic’s returning, helped the Serb to a break point at 4-3, which he converted with a spectacular defensive lob off Nadal’s serve-and-volley ploy and a measured ball into the open court. Although he was fortunate with a netcord at 30-30 when trying to serve out the set, there was nothing lucky or, indeed, less than emphatic about his ace down the T which closed it out.

Nadal never really succeeded today in matching Djokovic’s depth or accuracy, nor could he find the serve out wide that’s served him well this tournament. At 1-1 in the second, three consecutive forehand errors gave Djokovic three break chances at 0-40, and although the world No. 2 returned the favor with two backhand errors, a great return allowed him to convert for a break-of-serve lead which he never gave up.

Djokovic’s depth of shot kept Nadal running fruitlessly behind the baseline, while Rafa never succeeded in putting much pressure with his own return. It was a recipe for the kind of dominance we associate with Djokovic’s 2011 season, and although Nadal revived briefly in fending off the aforementioned first two championship points, the world No. 2 slammed another ace down the T for a third. He took it when Nadal, unable to penetrate his defense with a series of punishing inside-out forehands, fired the final one wide.

A combined total of 41 unforced errors to 28 winners testifies to the uneven quality of the match, but the fact that Djokovic had 19 of those winners emphasizes the success of his approach: Accepting the inevitability of some tired, end-of-season errors, but remaining committed to a relentlessly aggressive strategy. Having lost his No. 1 ranking to Nadal, this title—and the knowledge that a victory in the Davis Cup final would allow him to better Nadal’s 22-match winning streak from earlier in the season—will surely be ample consolation.