From golden to gutted.

That’s the emotional roller coaster — the risk factor — inherent in track relays.

One step out of line, one infraction however insignificant and non-impacting, and . . . GIVE THAT MEDAL BACK.

Which is what Canada’s 4x100 men’s squad had to do Saturday night, hand back the glory of gold some 2 1/2 hours after seemingly racing to victory.

Protest. Foul of foot. Result shift — victory to the Americans instead, silver to Brazil, bronze to Trinidad and Tobago.

Another big fat DQ for Canada in this tormenting, nemesis event.

Rewind and erase.

“We got DQ’d again,” said Peter Eriksson, head coach of Athletics Canada. “It’s because one of our runners ran on the line and you can’t do that in relays.

“It’s disappointing, but this happens all the time. It’s part of the game.”

Sadly, it happens a lot of the time to Canada’s men.

Their 4x grins had begun to slip ever so slightly as the sprinters stepped off the track, what seemed like a lifetime earlier, following their leisurely victory lap, each of them finding fashionable ways to wear the flag as victory accessory.

They’d just finished a CBC interview — first dibs for the national broadcaster — when an official advanced, speaking to the quartet in a quiet voice, sombre.

A frisson of anxiety flits across four faces.

Oh no. Not again. Say it ain’t so.

For half an hour, the foursome — Gavin Smellie, Andre De Grasse, Brendon Rodney, Aaron Brown (and in that leg order) — were Pan Am gold medal celebrants, joyfully swooping their arms at the cheering crowd and group-hugging. A season best of 38.06 for the 4x100, with the U.S. silver and Brazil bronze.

The rare triple gold crown for De Grasse, relay triumph added to his 100- and 200-metre splendour — a memorable 72 hours in this 20-year-old’s life.

Then came word there had been a protest, by the Americans.

They are all too familiar with protests and disqualifications, the men’s relay squad. There is entirely too much history.

2012 Olympics, London: Disqualified a few minutes after crossing the line in third because one of them (not part of the current team) had stepped foot over the lane line.

2014 Commonwealth Games, Glasgow: Out-of-zone exchange, DQ.

2015 world relays, Nassau: Out-of-zone exchange, DQ. That was also a chance to qualify for Rio 2016.

So you can understand why the déjà-vu apprehension.

“We felt like we ran a clean race,” insisted Brown. “So, we’re going to sit by and wait, see what they see, and hope for the best. But we’re pretty confident we had a clean race.”

De Grasse echoed that sentiment. “We just got to stay patient. We practised this. We had a training camp two weeks ago in Ottawa. We did well there and we know what we need to do. I felt like we did a good job and I think we came away with the gold medal.”

From Smellie, interestingly, not a word as the quartet of runners met with reporters in the mixed zone.

That protest focused on the baton exchange between De Grasse and Rodney, the Americans arguing Rodney had stepped out of his lane before receiving the baton.

“I seen Andre hit the mark and I moved,” said Rodney, straining to recall the exact details of the hand-over, even as the beads of exertion still remained on his skin. “And that was it. He got the stick in my hand, I ran around the curve, got the stick to Aaron and that was it.

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“I didn’t think there were going to be no problems.”

A decision pending left the four Canadians uncertain how to react. Some of the thrill was gone, at least for the moment, though they claimed confidence in the official outcome.

“We’re happy we did what we were supposed to do,” Rodney continued. “We’ve all got to stick around. There’s nothing else we can say except we’re happy we did it at home.”

More than an hour passed before word arrived that the American protest had been declined. Rodney had indeed run two steps on the line, but it was before he had the baton so didn’t count. “Until he got the baton, he’s not really in the race,” said Eriksson.

The Canadians were golden, whew.

And then, just about simultaneously, came news that, nope, they weren’t. Well, maybe. Or maybe not. Everybody stand down.

This time, the protests were aimed at leadoff runner Smellie — that he’d stepped on the line.

Those objections came from the U.S., Trinidad and Tobago, and Brazil.

Smellie had been part of all those relay teams which had been disqualified in the past — though he was never the culprit. He was, however, disqualified in his 100-metre heat here for a false start.

This time, the fault lay in his stars, after all, his foot clearly on the lane line.

The decision is final. Athletics Canada cannot appeal.

“You can see the guys ran super fast and did a phenomenal performance and that can never be taken away from them,” said Eriksson.

“At the world championships, it will be a clear race, it will be a faster start.”

So, one less medal on the toteboard and gold-times-two instead of gold-times-three for young De Grasse, the track star of these Games, undisputed victor in the 100 and 200 metres.

Think the global sprinting studs, most especially Usain Bolt, fastest man on earth at both distances and multiple Olympic gold medallist, will care about De Grasse’s Pan Am exploits when, if, they line up alongside each other for the 100-metre final in Rio?

“Um, I feel like, to them, they might not think this is a big Games, the Pan Am Games. The world championship is everybody in the world. I think I’ve got to go out there at the world championships and still make a name for myself. I feel like even though I’ve accomplished so much here, to other people it might not have been that impressive.

“So I’ve got to go out there at the world championships and make the final and get a medal.”

Is that all?