Thesauruses exhausted, all superlatives spent, the world’s press turned to the man himself to ask for help. “Usain,” the question came, “at London 2012, you spoke a lot about how you wanted to become a legend. But what should we call you now?”

Bolt paused, thought on it for a while. “Well,” he said, “someone said at a press conference last year that if I win these three gold medals, I will be immortal. And I kind of liked it. So I’m going to run with that: immortal.”

Like Michael Phelps, who had just beaten an Olympic record set in 152BC, Bolt may be racing the other athletes competing here, but he is not measuring himself against them. “I am trying to be one of the greatest,” he said, “to be among Ali and Pele”. As well as Phelps himself, and, oddly, Bob Marley, with whom he now seems to be vying for the title of most famous Jamaican.

Double-decker

They teach you at journalism school that double-decker buses are the standard unit for heights, as football fields are for areas, and Olympic swimming pools are for volumes.

But no one’s sure of the best measure for Bolt’s brilliance. Half an Ali? Two thirds of a Marley? One Pele? Bolt would not say whether he felt he was now more famous than Marley, more successful than Phelps, or what it meant to be compared to Pele and Ali.

It seems even his self-confidence has its limits, and in these conversations at least, he comes across as very modest. “I’m just waiting until after the Olympics, to see what the media have to say, all the media, to see if they will put me in that bracket,” he said. And on Phelps: “I could never pick who is the best, we are great in our different fields.”

If Bolt is thinking about his own mortality, it may because this week he, and we, have had the first intimations of it since he made his breakthrough at the Beijing Games in 2008.

His winning times in both the 100m and 200m are pretty similar to the ones set by other men in 2004 in Athens, where Bolt competed as a kid, and before he had redefined the possibilities of his sport. This year Bolt won the 100m in 9.81sec, whereas in 2004 Justin Gatlin did it in 9.85. And Bolt won the 200m in 19.78, whereas in 2004 Shawn Crawford did in 19.79. More tellingly still, for the first time in three Olympics, there were men competing against him here who could, and perhaps, should, have been capable of running as quickly as he did in both those finals.

Two of his competitors in the 100m final have personal bests better than Bolt’s winning time of 9.81sec: Yohan Blake and Gatlin, who has run quicker than that this very season. In the 200m there were three men who have run within two-hundredths of his winning time, and another, LaShawn Merritt, who ran four-hundredths quicker at the beginning of last month.

Compare that to Beijing in 2008, when there was nobody in the field who could run as fast as Bolt did to win the 100m or the 200m. Or London 2012, where Bolt himself was the only man who had ever beaten his winning time in the 100m, and only Blake, once, had ever run as fast as he did to win the 200m. Back then, most people could not dream of competing with him, let alone defeating him.

Here in Rio Bolt has been running the kinds of times his competitors can match. Some of that is circumstance. He spoke about the short turnaround between his semi-finals and final in the 100m. And the night of the 200m was a little cold and wet.

Getting older

But the big reason is that he feels he is getting on. “I’m getting older, so I don’t recover like I used to,” he said of the 100m. In the 200m he dearly wanted to break his own world record of 19.19. But he just could not do it.

All of which explains why Bolt is retiring even though he is still winning, why he is adamant that this will be his last Olympics, and that the World Championships in London next year will be his last major competition. Because immortals do not lose. And so long as he is undefeated he has, as he says, nothing left to prove.

“I have shown the world that I am the greatest,” he said. “That’s what I came here for, and that’s what I’ve done. So that’s why this is my last Olympics.” It seems this week that we have all been watching the lion in winter. Guardian Service