Twenty four minutes into Thursday's Premier League game, the England midfielder repaid the supporters for their tribute, floating a free-kick for Trevoh Chalobah to head home and set Chelsea on their way to a 2-0 win over their fierce city rivals.
The banner, Gallagher's latest goal involvement and his typical high-energy, tough-tackling performance seemed to send a message to Chelsea's owners that they should think twice if they really are considering selling him.
The U.S. owners of the club are reportedly interested in capitalising on the "pure profit" value of Gallagher who, as a product of the club's youth programme, would help to shore up Chelsea's finances.
The club have spent around 1.0 billion pounds ($1.25 billion) on players since the private equity-led takeover of the west London club two years ago, when Britain's government forced Russian tycoon Roman Abramovich into a sale.
Now, with a second season about to end trophy-less despite that huge outlay, with the only targets left being qualification for the Europa League or the even less glamorous Europa Conference League, Chelsea need to make their sums add up.
Gallagher has been on Chelsea's books since he was eight but his contract is due to expire at the end of next season, adding to the speculation that the hierarchy at Stamford Bridge might sell him this summer, just as fellow academy graduate Mason Mount was sold to Manchester United last year.
If the decision lay with the fans, Gallagher would be going absolutely nowhere.
As well as his assist against Spurs on Thursday, Gallagher scored the equaliser in a 2-2 draw away at Aston Villa on Saturday, adding to his case for a starting place in Gareth Southgate's England team in the Euros in Germany this summer.
"You can see in my starting 11, I think the whole season he was always there," Chelsea coach Mauricio Pochettino told reporters when asked about the importance of Gallagher to the team, adding he and other home-grown players "have the capacity in this type of game to give a little bit more."
Asked about the speculation surrounding Gallagher's future, he said he was not involved: "This is a situation that they need to fix between the club and the player."
