Here are two words that will send a shiver down the spine of every Chelsea fan: pure profit. In a world dominated by considerations around the Premier League’s financial regulations, they cannot help but fret about their homegrown talents being sold off to protect the bottom line.

Then again, needs must at Chelsea after a loss of £90.1m in the last financial year. Perhaps, even though it would be a dreadful idea, there is no option but to sell Conor Gallagher to the highest bidder this summer. If so, though, they would be doing their rivals a huge favour. After all, nobody could possibly have watched their deserved 2-0 win over Tottenham in a fevered, skittish London derby and concluded that the smartest thing a club striving for an identity can do next would be to reduce Gallagher to a faceless number in their next set of accounts.

The sense that players like Gallagher matter more was emphasised when a banner of him was lifted in the Shed End just before kick-off. “Chelsea since birth” was the message and it was not long before Spurs were feeling it. Gallagher, just as he was during last Saturday’s spirited comeback against Aston Villa, was everywhere. There was no chance he was going to let Yves Bissouma and Pape Sarr settle. The Spurs midfielders wanted time. Gallagher took it away.

He has thrived since moving into a deeper role, bringing out the best in Moisés Caicedo, leading to speculation that Chelsea’s midfield functions better without the injured and slower Enzo Fernández. No wonder Thomas Tuchel, the former Chelsea manager, thought Gallagher could be the new N’Golo Kanté. Few can match his pressing and energy. Spurs were overwhelmed.

Six minutes were on the clock when a rattled Sarr lost possession to Gallagher. Chelsea countered, Mykhailo Mudryk freeing Nicolas Jackson. Guglielmo Vicario saved but the tone was set. Unable to make their passes, Spurs would not gain a foothold before half-time. Ange Postecoglou fumed as the error count rose. The passiveness will have bothered him more than another concession from a set piece.

Not that he can continue to ignore such an obvious failing if he wants to keep his job. Mate, what if who we are is a team that folds every time the opposition have a dead ball? Is that a process? Or is it just self-defeating?

Twenty-four minutes in, we saw the only recorded example of Gallagher standing still. He hovered over a free-kick on the right, then had his deep delivery headed in by Trevoh Chalobah after Marc Cucurella’s sly block on Brennan Johnson was deemed legal.

But given how the goal was constructed – one academy product setting up another – it was hard to ignore the bittersweet vibe. Chalobah gets it. The underrated centre-back was almost sold last summer but he remains reassuringly reliable. Having given Chelsea the lead with an outstanding header, he would later make a crucial block on Sarr to deny Spurs an equaliser just before the interval.

There was pressure from the visitors at the start of the second half. Chelsea, though, stood up to it. When Son Heung-min looked like running through, he was stopped by Chalobah stretching out a long leg to dispossess him. Over on the right, meanwhile, it was impossible to fault Alfie Gilchrist. The 20-year-old right-back gave Son nothing.

“Alfie Gilchrist, he’s one of our own,” the home fans sang. But for how long? A quirk of the profitability and sustainability regulations is that the sale of academy products is encouraged as they register as pure profit in the accounts. Gallagher, out of contract next summer, is wanted by Spurs. There remains no sign of him signing a new deal.

The worry is that Chelsea’s owners have form for shifting the kids. Mason Mount has gone to Manchester United. Armando Broja is kicking his heels on Fulham’s bench. Ian Maatsen is on loan at Borussia Dortmund. Gallagher and the versatile, committed Chalobah could be next.

It is time for a rethink. Mauricio Pochettino wants to keep Gallagher. After several loans, this has been his breakthrough season. Gallagher flitted in and out last season, belief often elusive, but he has thrived under Pochettino. It does not matter that he can look untidy. He is not the most technically gifted player but he never stops running, is maturing from a tactical perspective and scores big goals. Opponents must hate him. He is a pest. For Chelsea, he is vital.

They need Gallager. They are losing Thiago Silva, whose departure will rob a young squad of another leader. Reece James, the captain, and Ben Chilwell, the vice-captain, are injured. The responsibility has fallen on Gallagher to lead and, in the absence of James and Chilwell, he has become the symbol of a team finally showing signs of playing Pochettino’s football. Selling him would be ridiculous.