If Jose Mourinho had got his way, Toby Alderweireld would be lining up in red on Monday night at Old Trafford, one of the experienced, expensive new signings he had asked Ed Woodward to make to try to make up the gap to Manchester City this summer.

While United asked Spurs about Alderweireld, they never made an acceptable offer. And on Monday the 29-year-old will likely be playing in Tottenham’s white instead.

The fact that that transfer never happened is only a minor detail, but it could yet have huge implications for the rest of this season. Not just because United failed to upgrade a key area, an area where they were obviously lacking in their 3-2 defeat to Brighton and Hove Albion last weekend. Their season will be worse for not having Alderweireld on their side.

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Even beyond that, the failure to sign Alderweireld fuels Mourinho’s sense of grievance against Woodward and has already been weaponised by Mourinho’s supporters as proof that he has been let down by his employers. When the post-mortems of Mourinho’s time at Old Trafford are written, the fact that Alderweireld was not signed this summer will feature heavily.

Why Mourinho is so desperate to sign Alderweireld for his United plan

And yet the most interesting and important aspect of the Alderweireld story for now is what happens to him next at Spurs.

Because Alderweireld and Tottenham looked to be heading for a divorce for some time. Alderweireld has wanted a big pay rise for years, to recognise his performances since joining in 2015 on a £50,000 per week salary. Plenty of Spurs players want pay rises, but his situation was complicated by a release clause that would allow him to leave in 2019 for £25million if no new deal was agreed.

The view in the Spurs dressing room was that Alderweireld was “the only player who had the club by the balls”, given that Spurs would have to either give him a new deal or sell him early if they did not want to lose him on the cheap.

So the expectation was that Alderweireld was heading for a move this summer, even before he missed three months of last season with a hamstring injury. When he came back in February, the partnership of Jan Vertonghen and Davinson Sanchez in a back four looked settled. Alderweireld, like Kyle Walker in 2017, could have been sold after losing his place in the first team. With Tottenham needing to sell to fund new recruits this summer, a deal with United for more than £50million might have suited all three parties.

But it never happened. And while Spurs want to find a new club abroad for Danny Rose in the next week, there is no prospect of Alderweireld leaving. Last Saturday Alderweireld was brought back into the Spurs first team for the 3-1 defeat of Fulham, as Pochettino went back to a back three. It was a surprising return to the fold for a player whose Tottenham career looked to be over.

If Alderweireld can convince Pochettino that he is as fit and sharp as he was before his hamstring injury, then he could yet be reintegrated into Pochettino’s plans. Although he will be conscious that Danny Rose only started nine league games last season after trying to force a move last August.

The likeliest outcome is still that Alderweireld leaves next summer, for the clause price of £25m, at which there will surely be buyers for him even at the age of 30. But until then he is in an unusual position, still at Spurs having tried to leave, on the fringes of Pochettino’s plans, with the chance on Monday to prove to Manchester United why they should have spent the money on him.