Behind an untouchable serve, Milos Raonic makes the semi-finals in Tokyo

The only thing Milos Raonic had to be unhappy about Friday in the quarter-finals of the Rakuten Japan Open was the way he returned serve.

And rightly so. It was not, to say the least, his best day in that area.

But the way the 23-year-old Canadian was serving, all he needed was to make a couple of returns at the right time. And that's exactly what Raonic did in a 7-6 (8), 6-3 victory over the game, but overpowered Denis Istomin of Uzbekistan.

Raonic will play Gilles Simon of France in the semifinals on Saturday.

There was one single, solitary break point – on either side – in the one hour, 19-minute match. It was earned by Raonic late in the second set. And he made it.

Early on, Raonic's frustration at his inability to put Istomin's serve – which was coming in around 200 km/h, no more than that – into play was palpable. At one point, at 5-5, after yet another backhand return dribbled into the net, he even yelled out "Ajde!!" – the Balkan equivalement of "C'MON!" but usually used under more far positive circumstances.

Raonic's return struggles often mean that even the matches he wins with what appear to be relatively straightforward scorelines often hinge on the thinnest of margins, just a moment here and there. And that was the case Friday.

He had a mini-break in the first-set tiebreaker and had been volleying well the entire set ... until 5-4, when he netted a forehand volley to give the mini-break back. But at 8-8 in the tiebreak, Istomin cracked. He double-faulted, dropping both his head and his racquet in dismay.

Istomin did the hard work on the ensuing set point, getting a 233 km/h serve out wide back into play – a serve that speedy under any circumstances is impressive; one that's hit out wide in the court at that speed is insame – but netting a routine backhand.

The previous encounters between the two, both on the fast indoor court at the now-defunct event in San Jose that was so good to Raonic earlier in his career, both featured first-set tiebreaks. On those occasions, Raonic won going away in the second set.

This time, Istomin hung in much longer.

But when it mattered, Raonic got the job done. At 3-4 on Istomin's serve, 15-30, he made the return when he most needed it. On the next point – the first break point of the match by either player – he made another return. Perhaps half-shocked by that, Istomin missed an easy forehand.

The way Raonic was dealing, it was unlikely he would be broken when he served for the match. Until that point, he was a perfect 34-for-34 when his first serve went in. The only real suspense centered around whether the Canadian would be able to shake hands with that perfect slate intact.

He very nearly did. A 227 km/h ace. a 219 km/h delivery and a winning forehand. A 225 km/h ace. He was 37-for-37, and he was at match point.

After just missing an ace to close it out  Raonic had a momentary lapse of sanity and went for a 210 km/h  second serve, which landed halfway up the net.

Istomin had one more chance to break the streak. He took a 229 km/h delivery – one of Raonic's fastest of the match – got it in play, and hit a forehand winner.

But it was only a momentary reprieve. One more big serve, and Raonic was through.