Third time unlucky for Milos Raonic in the Tokyo final, as he loses another close one to Kei Nishikori

A rivalry for the next generation has been born this season between a 23-year-old, big-serving Canadian and a relentless 24-year-old from Japan.

It doesn't have much history yet. And it is still building its charisma. But it sure has been hotly contested.

Milos Raonic and Kei Nishikori played the fourth installment of their season series in the Tokyo final Sunday before a sold-out crowd of 10,000 that, save for the few Raonic supporters, was overwhelmingly in the corner of their hero. And in the end, an exhausted Nishikori pulled it out, 7-6 (5), 4-6, 6-4, his astonishing ability to return Raonic's serve once again narrowly winning out over Raonic's ability to blow it by him.

[Photos: Nishikori defeats Raonic at the Japan Open]

Raonic had 22 aces to Nishikori's one, one double-fault to Nishikori's four. But in the end, their effectiveness on serve, by any measure, was a near dead heat.

That 2012 final against Nishikori (Raonic lost the final last year to Juan Martin del Potro) followed a similar pattern, with Raonic losing the first set in a tiebreaker and winning the second. But he lost the third set 6-0 two years ago. So you can see where he's coming from there.

That was their first meeting. Since then, they have played four more times – all this season. The only one Raonic was able to pull off was on the grass at Wimbledon, in four sets in the fourth round. Their five-set epic at the U.S. Open last month ended at 2:26 a.m. and, just like the Tokyo final, was won and lost on the smallest of margins.

Raonic did little wrong in the first set. After overcoming a mini-break in the tiebreaker on two occasions, he fell victim to a wondrous return by Nishikori on his first set point at 6-5. Raonic bombed it at 222 km/h out wide to Nishikori's backhand. But Nishikori, as he so often can do, managed to get his racquet on it. Certainly Raonic wasn't expecting it, and it was an awkward shot to handle. The Canadian managed a slice down the line, but it was an easy passing shot for Nishikori. And just like that, all that hard work was for naught.

The Canadian stayed patient, though. Certainly he showed some frustration with missed returns. And most definitely his money shot – the inside-out forehand - was far below its usual standard.

But Nishikori has had a jam-packed two weeks after a short break following his run to the U.S Open final. It began in Hong Kong upon his arrival in Asia, where it was a whirlwind of promotional appearances. Then he won an ATP Tour 250-level tournament in Kuala Lumpur, Malaysia last week.

He returned home, to Japan, a place he has all but abandoned simply because he's such a big deal, he can no longer go anywhere without being mobbed. As the focus of all the attention all week, as he filled the 10,000 seat stadium for his matches, the 24-year-old squeaked out a victory in a third-set tiebreaker over Benjamin Becker on Saturday in the semi-finals. At some point, there was going to be a drop.

It came in the second set. And Raonic took full advantage of it.

He earned the first break point of the match in the opening game, but couldn't convert. At 2-2, he earned another one, but let that one fly by as well. At 3-3, Raonic earned three more and, finally, Nishikori gave him the error he needed. He closed it out without incident, and his groundstrokes were beginning to land.

They had to; unlike his previous opponents, Nishikori was giving him few opportunities to get to the net. Raonic won just one point up there in the first set, and just one in the second set.

The third set was, again, played on a tightrope.

The moment of truth, in retrospect, came for Raonic at 3-3. Often called the crucial seventh game, it was one in which Nishikori gave Raonic every opportunity to take control

In the first three points, Raonic had second serves clocked at 144, 141 and 147 km/h to work with. He missed the first backhand return by a mile, dumped the second one in the net, and did nothing more than put the third one right down the middle of the court. But from 40-0, Raonic pushed it to deuce. Finally, Nishikori put in two consecutive first serves, and got himself out of that one. It was Raonic's best chance.

Serving to stay in the match, his 230 km/h deliveries were nowhere to be found. Raonic's first two serves didn't even hit 200 km/h, and Nishikori was all over them.

Match point was a microcosm of the match. Raonic's first serve came in at 229 km/h, Nishikori got it back into court, and Raonic's final forehand let him down.

Afterwards, the exhaustion was clear on Nishikori's face. He was emotional, tears running down his cheeks as he went over to his supporters, which include coaching consultant Michael Chang. He likely felt exponentially more pressure Sunday in Tokyo than he did in the U.S. Open final.

But Nishikori withstood it. Just as he did in New York, even when he seemed he was running on the scarcest of fumes, he found a little extra reserve of energy and will that got him over the finish line.

"I hope that was a final everybody could enjoy," Raonic told the crowd in Tokyo. "To be honest with you, I’m sick of being a finalist here three years in a row."

He laughed, and once the translation went through the crowd, got one in return.

The Canadian showed a lot of good things over the week. He served rockets. Until the final he stayed in back-court rallies impressively. He showed some terrific work at the net when he had an opportunity to attack.

But Raonic's lack of pressure on his opponent's second serve is a part of his game that remains a work in progress.

In a matchup with such tiny margins, that made the difference.