Has Milos Raonic reached the end of the line?

The last time Milos Raonic reached the fourth round of the U.S. Open, it was a capital-E Event for Canadian tennis.

It was 2014. Raonic had announced himself earlier in the summer with a semi-final appearance at Wimbledon. He gave the impression of a young man on the cusp of a breakthrough.

That match, against Japan’s Kei Nishikori, started late and went much later. By the time they got to the fifth set, the upper bowl had emptied out. The only people left up there were the night cleaners, waiting for their shift to start. It ended just past 2:30 a.m.

But if you are Canadian and any sort of sports fan, you were probably still up. It was that big of a deal.

The local kid lost that night, but the final word on the matter went to Stan Wawrinka. Calling Raonic “a little bit different” than the rest of tennis’s then-young generation, the Swiss judged, “He’s there.”

Raonic, now going on 28, is no longer young. As it turns out, he was never quite there – not there there. And very few people are willing to wait up late for him any more.

Four years, a few highlights and many injuries later, Raonic made the fourth round in Flushing Meadows again on Sunday.

This was not a moment of national anticipation. Not because no one believed Raonic could win, but because of the opponent and the sort of match his presence suggested.

John Isner is Raonic’s American doppelganger in many ways – tall, immobile, a server of immense and tedious power, as well as a small disappointment to his countrymen.

Both carry the flag for their national game. Both have a tendency to get all tangled up in it whenever too many people start paying attention to them. That would be this point in a major tournament.

To Isner’s credit, he has always worn his gawky on-court approach and tendency to lose miserably to anyone half-decent with a certain lightness.

Isner, 33, knows what he is – a very-good-never-going-to-be-great jobbing professional athlete. It’s not bad work if you can find it. Isner seems to get that.

Raonic gives off a very different impression – of someone who cannot understand why it isn’t working out.

He’s tried almost as many personas as coaches over the years, which is to say a lot of them. We have now entered the dark Milos phase of things, wherein Raonic gives off so little feeling on the court that it creates its own sort of emotional intensity.

No fist pumps. No speaking. No looking at his box. No nothing at all.

That worked for exactly one set on Sunday. Raonic isn’t able to surprise anyone with his tactics – serve the ball hard, then hope – but he can catch someone out with his focus. His first set was virtually error free.

Coming off a best-of-season performance against Wawrinka in the Round of 32, Raonic’s early form might’ve been enough to deeply unsettle another competitor.

But Isner is accustomed to being bad for long stretches and still managing to win. That’s precisely how he does it. He buffets you with that catapult of a serve until you lose your will to go on. He hasn’t won much at tennis, but he seems to play more tennis than anyone in history.

So despite his own inability to play it cool – fist pumping every winner, looking up at his box every 10 seconds for encouragement – Isner was not fazed.

He won the second and third sets. Raonic rallied in the fourth. Then the familiar physical breakdown. Before the beginning of the fifth set, a physiotherapist was out on the court twisting Raonic around like a human hot-pocket.

It was either his hip or his back or the part where his hip meets his back. Take your pick. Raonic has pulled them all.

Isner plowed him over in the fifth – 3-6, 6-3, 6-4, 3-6, 6-2 – and that was that. Raonic’s tennis season isn’t over, but now that the Grand Slams are done, it really is. He hasn’t made the semis of a major in more than two years. He hasn’t won any sort of tournament in nearly three.

Whether he wants to see it like this or not, Raonic is no longer on a path to become the next Wawrinka or Juan Martin Del Potro – the sort of player who’s never been the favourite, but has managed to win the big one once or twice.

Instead, Raonic is an Isner. He has one skill. That skill is good enough to make him a lot of money, but it’s never going to bring him glory. And all of that is contingent on keeping a rebellious body on board with the program, something that gets harder with each passing year.

Raonic is the sort of player people like, but don’t expect much from. He is the sort people will stop to watch, but only if the match is on in the afternoon and doesn’t conflict with another, better one.

After a few years spent stamping our feet over Raonic’s inability to elevate his game beyond its initial promise, maybe that’s enough.

Four years ago, it was a big deal that a Canadian man was on the cusp of the second week at the U.S. Open. Oddly, it felt like an even bigger deal than Raonic’s Wimbledon final a couple of years later. Because you were getting in on something early – before the bandwagon jumpers heard about it.

Raonic is old news now, and no one believes any more. At least, not that he can win a major.

But he’s still the best we’ve ever produced, and he’s still making an impression out there. Sunday’s first set was more sweet than bitter as you thought to yourself, “Imagine if he played like this all the time.”

Every once in a while, when he’s feeling it, Raonic is even still fun to watch.

But that’s us. We have the luxury of finding perspective on Raonic’s career in the midst of it and what it’s all meant.

Raonic doesn’t get the same benefit. And as a result, he does not look like he’s having much fun out there at all.