Who will rescue Frankie Dettori as the twilight zone looms again?

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"For someone of that class, to see them wander off into a twilight zone, it was just not palatable that that could happen." The speaker is John Gosden, reflecting on his thinking when he took in Frankie Dettori as his stable jockey at the end of 2014.

Now, Dettori has been cast out and the twilight zone looms once more. He's eight years older, 51, and everyone's aware that he has not been at his best these past couple of months.

It's the middle of the season, everyone has their jockey arrangements in place. Dettori is known for requiring careful handling and it seems he's finally at odds with the trainer who was famed for being able to manage him and keep him happy, focused and motivated. Who will stick up for him now?

I hope someone will do it, not least because I've just been rewatching 'Dettori', the feature-length documentary released in November and still available through Sky – possibly also through other outlets. It's in the nature of these things that, even though you know you're getting a favourable take on the subject, you end up rooting for them.

It was from the documentary that Gosden's line at the top of this story was taken. As Dettori chats to camera about what it meant to be rehired by his old friend and offered a fresh chance at the very top of the game, he becomes overwhelmed with emotion.

"I couldn't wait for the season to finish and start the next year. I was so excited. After two years being no one, I'm back and there's this really overwhelming feeling of warmth. It's amazing."

He even attempts an impression of Gosden's distinctive speech, recalling the trainer's opening words in the phone call that brought them back together: "Hi, matey..."

It's terribly poignant to watch, now that they've split. The movie reminds you of how good and strong their alliance was.

Saddest of all is the impression that what has ended is not just their working relationship but their friendship as well. What can have happened to bring us to this pass?

Dettori has given Gosden cause for a whole range of emotions, including exasperation, over the years, but a rupture never seemed on the cards because there was always understanding from the older man. There was quite a large measure of tolerance, bolstered by faith that the brilliant jockey would re-emerge in short order and remind everyone of his qualities.

So it might have been expected that, if Gosden were one day persuaded the Dettori skills (or application) were finally in irreversible decline, the trainer would let him down gently. They would stagger through the season somehow and call it quits with a party to celebrate the great ride they'd shared.

Instead, repeated criticism during the biggest meeting of the year, even in the moments after a Group 1 victory. Firmly expressed, with no modifying jocularity. The headmasterly: "Is there a reason you took him back so far?" within earshot of others after the Gold Cup. The sarcastic use of "our hero". Find the fondness in that.

Something has gone wrong between them, something more than a few disappointing races. Details will ebb out in due course. Like everything else in horse racing, the answer will be multi-factorial.

It would hardly surprise if there were some tension over future riding arrangements at Clarehaven. Thady Gosden, who is half Dettori's age, was added to the licence last year and must have his own ideas about jockeys. One paper reported at the weekend that he is a friend of Oisin Murphy. Murphy is close to the owner of Stradivarius and watched the Gold Cup with him in the Ascot paddock.

This is just my speculation. Since at least one firm is taking bets on who the Gosdens' next retained rider will be, others will also be speculating. Of course the answer might be "no one", for years, so I wouldn't be rushing to tie up money in that market.

Back to that excellent documentary, full of insights into our hero and other members of his family, a film which left me with a deeper understanding of the forces that shaped him and no small admiration for how he has handled a very testing relationship with his father. It also reminds the viewer that Dettori has been in something like his current position twice before. Back in the 1990s, he quit Luca Cumani's employ to ride in Hong Kong and then lost the Hong Kong offer after being caught in possession of cocaine.

Then, at the end of 2012, he lost his job with Godolphin and got a six-month riding ban for a cocaine positive. The next year, he rode just 16 winners at a strike-rate of eight per cent.

It will be noted that he was very largely the author of his misfortune on those occasions. Perhaps it is true again now.

During the second of those slumps, he was confronted by his wife, Catherine. "All your life, you're telling me that you're good. Now that we need you, show me how good you are!"

With tears in his eyes and a wry smile, Dettori tells the camera: "Strong words. To hear that from your wife ... Heavy salad, let me tell you. That really hurt me inside. I thought, right. I'll show you."

Show us again, Frankie! Lift yourself out of this hole and be great. Racing is so much more fun when you're on top of your game.

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The Front Runner is our latest email newsletter available exclusively to Members' Club Ultimate subscribers. Chris Cook, a four-time Racing Reporter of the Year award winner, provides his take on the day's biggest stories and tips for the upcoming racing every morning from Monday to Friday