Frankel – a horse for all seasons or merely the latest instant Pegasus?

The spool has never been unrolled anywhere near its limit, and just about the only boundaries Frankel has ever crossed are the spectral ones bequeathed by champions past. But his superiority, within that comfort zone, has been such that many seasoned judges soberly attest there may never have been a better thoroughbred.

No less a witness than André Fabre, 23 times champion trainer of France, this week joined their number. Frankel seems almost certain to be retired after his 14th start, at Ascot tomorrow, and Fabre implored a sell-out crowd to savour the privilege. "It is like looking at a museum piece," he said.

And while those who have supervised Frankel's career have been reproached for a conservative approach – keeping him at the same distance almost throughout, and declining to seek out fresh opposition abroad – then it may yet prove that the Qipco Champion Stakes will expose him to a fitting new challenge. For the primal energy that has so far withered all in its path must now be measured against the elements themselves.

The autumn deluges guarantee the deepest going Frankel has ever encountered. Moreover, the rival who will attempt to cross the abyss at its narrowest point – the rags-to-riches French star, Cirrus Des Aigles – has a history of gliding clear of his rivals, à la Frankel, whenever he has run through the mud.

Sir Henry Cecil, Frankel's trainer, admits that deteriorating conditions could conceivably disclose an Achilles' heel in Frankel. "I'm pretty confident he will be fine in soft ground," he said. "But if it's heavy, we are in no man's land. He has never encountered it and, with his action and turn of foot, I cannot be sure that he would appreciate it. And Cirrus Des Aigles and Nathaniel will go in the ground and get the trip really well. They have to be really respected."

As usual, however, few others have been tempted even by place money, and Frankel's own pacemaker, Bullet Train, is among just five others declared. On the assumption that he will indeed be retired to stud by his owner – no decision has yet been made, albeit the sport is already indebted to Prince Khaled Abdulla for persevering a year longer than many expected – then one of his rivals can neatly close the circle. For the half-length that divided Frankel from Nathaniel, on their debut at Newmarket in 2010, remains the narrowest margin of all his 13 wins. Nathaniel himself has since proved top-class, by any ordinary accounting, but his trainer, John Gosden, says it would be "daft" to entertain getting any closer this time.

William Buick, Nathaniel's jockey, similarly captured the mood of the professional community. "Frankel has been a joy to watch," Buick said. "Obviously, we'll all be trying to beat him – but he is unbeatable. On Saturday I'm sure he'll do what he always does. And, deep down, I hope he does. Because if he goes out on a high, it would be fantastic for racing. We're there to beat him, but as Frankie Dettori was saying to me last night: 'Get real – it's not going to happen.' I'm still young. But I think we've been really lucky to have this horse around."

Buick paid tribute to the cool of his rival, Frankel's jockey Tom Queally, which sometimes seems in inverse proportion to the hoopla around his mount. At 28, Queally is already trying to reconcile himself to the vacuum that beckons, when Frankel is no longer around. "He's been a huge part of my life, and raised my profile no end," he said. "But it's tricky, because I know that even if I'm lucky enough to win a Derby in future, the first question put to me will be: 'How does he compare to Frankel?' So I've tried to stay as grounded as I can."

Rumours that Frankel might yet be kept in training doubtless owe much to the still greater sense of loss anticipated in his trainer. In showing such fortitude during a six-year battle with cancer, Cecil has found palpable succour in this horse. "Frankel has been an inspiration and challenge, which I needed so badly," Cecil said candidly. "Through my illness, I feel that help from my wife Jane and the determination to be there for Frankel has helped me so much to get through the season."

He even ventured that the colt, with maturity, is only now entering his prime. "I was very pleased with Frankel's final piece of work," Cecil said. "He gives the impression he is better than ever, and still improving."

One way or another, it seems as though Frankel, having coped serenely when finally stepped up in trip at York in August, is set to be retired without exploring the full reach of his talent. Mind you, even if his connections had actively gone looking for trouble – perhaps against the top American horses, on dirt, in the Breeders' Cup Classic – then his place in a pantheon stretching back three centuries would necessarily remain a matter of conjecture.

Since 1977 handicappers have made scrupulous efforts to give formal, objective expression to equine merit. But even contemporaries can reach wildly different conclusions. As things stand, Frankel is officially rated 140 – the same as Shergar, but 1lb below the 1986 Arc winner, Dancing Brave – but Timeform, the respected analysts, have given him an off-the-charts rating of 147.

All such gauges are contingent on the quality of the opposition, and the indolence or extravagance with which any given champion dismisses inferiors. Does a Test average of 50.23 make Viv Richards a better batsman than, say, Denis Compton on 50.06? Of course, Frankel sooner approaches equivalence with Bradman's 99.94 – but the same would have to be allowed of Secretariat, Sea-Bird or Ribot, never mind others beyond living memory. Racing has a culpable habit of exalting its latest paragon as the best ever. But the mystery that defines them all, Frankel included, can no sooner be expressed as a number than a scent can be caught in a net.

Frankel's immaculate career: 13 races, 13 wins

1. 13.8.10: 1st of 12 In a maiden race, over 8 furlongs at Newmarket, beating Nathaniel half a length, at 7-4 favourite.

2. 10.9.10: 1st/3 Conditions race, 7f Ascot, beating Rainbow Springs 13 lengths, 1-2 favourite.

3. 25.9.10: 1st/5 Royal Lodge Stakes, 8f Ascot, beating Klammer 10 lengths, 3-10 favourite.

4. 16.10.10: 1st/6 Dewhurst Stakes, 7f Newmarket, beating Roderic O'Connor 2¼ lengths, 4-6 favourite.

5. 16.4.11: 1st/6 Greenham Stakes, 7f Newbury, beating Excelebration 4 lengths, 1-4 favourite.

6. 30.4.11: 1st/13 2,000 Guineas, 8f Newmarket, beating Dubawi Gold 6 lengths, 1-2 favourite.

7. 14.6.11: 1st/9 St James's Palace Stakes, 8f Ascot, beating Zoffany ¾ length, 3-10 favourite.

8. 27.7.11: 1st/4 Sussex Stakes, 8f Goodwood, beating Canford Cliffs 5 lengths, 8-13 favourite.

9. 15.10.11: 1st/8 Queen Elizabeth II Stakes, 8f Ascot, beating Excelebration 4 lengths, 4-11 favourite.

10. 19.5.11: 1st/6 Lockinge Stakes, 8f Newbury, beating Excelebration 5 lengths, 2-7 favourite.

11. 19.6.12: 1st/11 Queen Anne Stakes, 8f Ascot, beating Excelebration 11 lengths, 1-10 favourite.

12. 1.8.12: 1st/4 Sussex Stakes, 8f Goodwood, beating Farhh 6 lengths, 1-20 favourite.

13. 22.8.12: 1st/9 Juddmonte International Stakes, 10f York, beating Farhh 7 lengths, 1-10 favourite.

Best of the best: Top horses of modern era

Official ratings since classifications began in 1977:

141 Dancing Brave 1986

140 Alleged 1978; Shergar 1981; Frankel 2012 (current)

138 El Gran Senor 1984

137 Three Troikas 1979; Generous 1991; Peintre Celebre 1997

136 Troy 1979; Suave Dancer 1991; Sea The Stars 2009

Turf account

Chris McGrath's Nap

Neige D'Antan (7.50 Wolverhampton) Looks feasibly treated at this lowly level, doing well to get so close to one who had controlled a steady pace on her last visit here.

Next best

Ovett (6.50 Wolverhampton) Showed plenty of dash in better company last time, before fading inside the last, and should be suited by drop in trip for his nursery debut.

One to watch

Louis The Pious (David O'Meara) Contested a hot pace on his debut for a new stable at York last weekend and did well to rally and force a photo.

Where the money's going

Cheltenham stages its first meeting of the season today, and Ambion Wood is 16-1 from 25-1 with Paddy Power for the RSA Chase.