Tottenham earned a big win over Brighton after a change in system from Antonio Conte but there is every chance the head coach's 3-5-2 may yet prove a one-off.
Harry Kane's first-half goal on the south coast strengthened Spurs' position in the top four and opened up a six-point gap to fifth-placed Newcastle.
Conte switched from his preferred 3-4-3 to a 3-5-2 for the first time since January 19 (in the Steven Bergwijn game at Leicester), with Yves Bissouma coming into the midfield against his former club and Richarlison dropping to the bench.
It was a response to Dejan Kulusevski's continued absence with a hamstring strain, as well as perhaps an acknowledgement that his side have struggled to control games this season and occasionally been overrun - as in last weekend's defeat at Arsenal.
Matt Doherty also started for the first time since April for the suspended Emerson Royal, despite Conte suggesting on Monday that the Irishman was still not ready, meaning this was an XI Spurs fans have long been calling for.
There was early promise in the new set-up, and Spurs benefitted from having an extra body in midfield against Roberto De Zerbi's well-drilled Seagulls side.
In the opening exchanges, Conte's team were more adept at winning the ball back and had much more possession than in recent games. With Bissouma anchoring the midfield three, Pierre-Emile Hojbjerg and Rodrigo Bentancur had a platform to push forward, and both were involved in the build-up to the winning goal.
Bentancur forced a brilliant one-handed save from Robert Sanchez and from the resulting corner, Hojbjerg recycled the ball back to taker Son, who whipped in a low cross from the right for Kane to flick home. It was a smart finish from the England captain, who had to stoop low to score his eighth goal in nine League appearances.
But Brighton were much the stronger side after the goal, and before half-time Hugo Lloris was forced into smart saves from Moises Caicedo and Danny Welbeck, while Lewis Dunk and Solly March both went close.
After the break, the Seagulls continued in the ascendency, and Spurs had to cling on in the final 10 minutes, with a series of last-ditch clearances and challenges, including a crucial Doherty block on Leandro Trossard.
Bissouma's booking midway through the first half for a clumsy, late challenge on Alexis Mac Allister somewhat limited his effectiveness, and Conte introduced Richarlison for the Malian with 20 minutes to play, reverting back to 3-4-3.
It made little difference to the overall pattern of the game, with Spurs continuing to look dangerous on the counter-attack but sorely missing a final ball. Time and again they managed to repel a Brighton attack, only to break forward and fluff their lines in the final third.
Kane went closest to a second goal when he rolled his man but dragged an effort wide of the far post, while Son had a trademark curling strike ruled out for a close offside.
Ryan Sessegnon, who was named player of the match by broadcaster Sky Sports, got himself into some fine positions but aside from an early cross for Doherty, his execution was erratic. Doherty understandably looked rusty, striking Sessegnon's cross into the ground and over the bar and miscuing when set free by Bentancur.
Ultimately, while the change in system made Spurs easier on the eye and more in control for 25 minutes here, their problems were familiar. Without Kulusevski, they are lacking a touch of finesse in the final third, while it is doubtful if their wing-backs have the required quality for a Conte side.
The head coach may stick with the 3-5-2 system midweek against Frankfurt but this game was not decisive evidence that it is the way forward for Spurs.