It took only 15 minutes and one misdirected header for Mauricio Pochettino to have second thoughts.
If Manchester United’s Jesse Lingard showed here three weeks ago how a ‘false nine’ can be used to devastating effect, Lucas Moura demonstrated in the first quarter of an hour on Saturday what happens when the role is taken to the extreme.
Namely, so false as to be virtually invisible.
But then the Brazilian re-appeared, unmarked and under no discernible pressure.
Six yards from goal, he rose to meet Erik Lamela’s clipped cross. The Wembley crowd rose in expectancy, almost certainty.
But Lucas sent the ball wide of the near post and Pochettino had seen enough – moving Son Heung-min inside and pushing Moura out to the left until half-time.
This was Spurs’ fifth game without Harry Kane, and the manager’s fifth different attacking unit in that time.
Back three, back four, midfield diamond, two up top – each week Pochettino has tweaked his team and his system in search of a winning formula while Kane recovers from an ankle injury which could keep him out until March.
Since that defeat by United they have been dumped out of two domestic cups, while two late winners have saved his side from further setbacks in the league.
By the final whistle, that had become three. Another system, the same nail-biting result.
On Saturday, they started in a 4-3-3, with Moura flanked by Son on the left and Erik Lamela.
But following Lucas’s missed header, Son moved inside and the TV cameras turned to Fernando Llorente.
It’s said you don’t know what you’re missing until it’s gone, and so often in football a player’s stock is never higher than when they’re not on the pitch.
It’s true of Kane and on Saturday it seemed true of his understudy as Spurs consistently found openings with balls from wide.
First Lucas sent his effort wide and then Lamela saw a header come back off the bar.
Llorente had started four games in a row until this one, netting with his head against both Chelsea and Watford. What Spurs fans would have given to put him on the end of one of these crosses.
Come the second half, however, Lucas was given a second chance down the middle.
But within 15 minutes Pochettino had lost patience once more.
As Spurs pressed for an opener, none of Lucas, Son or the onrushing midfielders could turn home Kieran Trippier’s low cross.
Again the spurned opportunity proved the catalyst for change.
Llorente was called back to the bench, sent on for Lucas and promptly won his first aerial battle.
His introduction gave Spurs a new focal point and provided a lift to an increasingly frustrated home crowd.
With 20 minutes to go his chance came. Eriksen floated an inviting ball into the box and Llorente peeled off the back of Fabian Schar. But his header flew harmlessly over as the Spaniard bemoaned the interference of the sun. If only he’d grown up in a warmer climate like Spain.
Then, after Matt Ritchie had turned away Eriksen’s flicked effort, it was beginning to feel like one of those days – whatever Pochettino tried, whatever system he deployed and whoever the chances fell to, nothing would go in.
But then Llorente laid the ball off for Son, who fired at goal and Martin Dubravka did the rest.
Whether the chance had come courtesy of a Llorente handball was debatable. Whether Dubravka should have done better was undeniable. But Spurs didn’t care – it was the slice of luck that had deserted them all day.
Kane may be away for some time yet but for the second time this week Son has proved a much-needed returning hero. Who knows what his manager will try next?