As the Whites will hopefully discover next season, against the best, you have to capitalise when on top.
The Gunners wriggled off the hook, scoring through Reiss Nelson, and another Leeds FA Cup campaign ended at the first hurdle. Marcelo Bielsa’s side have bigger fish to fry between now and May, but they can take confidence as well as lessons from last night’s 1-0 defeat.
Both these teams are learning to play the Bielsa way, but whereas this is Leeds’s second season under the Argentinian, Arsenal just into their third week of Mikel Arteta – a disciple of Pep Guardiola, who in turn is a huge admirer of the Leeds manager.
Everything about the first half was good from a Leeds perspective, apart from the 0-0 scoreline. It took some good goalkeeping and a Patrick Bamford shot against the crossbar to ensure that the Whites’ 15 first-half shots yielded no goals.
They would pay for it in the second half.
As half-time approached, the 8,000 or so away fans sang about how their team were taking the mickey, while Sokratis Papastathopoulos was urging Arsenal’s to calm down.
Arsenal tried to knock the ball around with assurance, but Leeds managed it. Both stand-in goalkeepers wanted to play their part, but whereas Emi Martinez gave the ball away, debutant Illan Meslier looked as composed with it at his feet as he had catching Nicolas Pepe’s eighth-minute shot.
His touch from an unsympathetic Douglas pass was exquisite enough to be that of a multi-million-pound Premier League midfielder, not a rookie Championship goalkeeper.
Martinez and an inexperienced bench apart, Arteta fielded what was arguably his strongest XI, yet the goalkeeper needed to make a string of saves.
Barry Douglas was making only his fifth start of the season at left-back, but you would never have guessed. Mateusz Klich played with a tigerish hunger in midfield and whether staying wide on the right or cutting inside, Jack Harrison was a constant pest.
Leeds were playing like a team with a plum fourth-round tie on the line, not an arduous trip to Bournemouth, as they found out shortly before kick-off.
Klich collected the ball when Rob Holding gave it away in the seventh minute, forcing Sokratis into an excellent tackle as Arsenal struggled in the face of the Whites’ ferocious pressing game.
With Harrison leading, Arsenal’s left-hand sidewas most under pressure, and he brought Martinez’s first save of note in the 15th minute.
Martinez did well to keep out Harrison cutting inside, and was fortunate Ben White could only glance a Kalvin Phillips free-kick at him.
By then, Bamford had smashed an excellent Ayling pass against the crossbar.
For all that, it looked like the Premier League team might punish Leeds for not landing the killer blow when White’s mistake let Alexandre Lacazette in after 24 minutes, only for the centre-back to produce a recovering tackle.
It was Sokratis who worked his goalkeeper the hardest, heading under pressure from Ezgjan Alioski. Robbie Gotts, Leeds’ other debutant after 29 unused substitute appearances, lifted a shot from Klich’s cut pass over.
Arteta looks well acquainted with a hairdryer, and the way his team started the second half suggested he used it in the interval. Arsenal started the second half as hungry as were timid in the first.
Nelson turned White within the first couple of minutes, only to be crowded out by Douglas and Phillips.
With Lacazette hitting the corner of the woodwork from a 50th-minute free-kick, then kept out by Meslier at the end of a sweeping move, it felt like a Gunners goal was coming.
Pepe and Lacazette combined on the right and Gaetano Berardi diverted the ball into Nelson’s path to put his side in front.
Well as Leeds had played, and even with 35 minutes left, it felt decisive.
Of all the numerous bookable tackles Granit Xhaka was involved in, it was the one on him – by Klich – which got the card out of Anthony Taylor’s pocket.
Inevitably, the first video assistant referee decision in Leeds’ history was a bad one. Taylor could not have had a better view of Lacazette’s kick at Berardi, yet neither he not VAR Stuart Atwell thought it worthy of a yellow, never mind a red card.
The good news for Leeds was they avoided a sending off that was starting to look likely after something of nothing by the corner flag involving Harrison, Douglas and inevitably Xhaka when Atwell pressed the rewind button again.
For all that the Whites pushed for an equaliser, and even though their fans sang of how proud they were of the men in powder blue, the only big save left in the game was Meslier’s from substitute Gabriel Martinelli.
Arsenal: Martinez; Papastathopoulos; David Luiz; Holding; Kolasinac; Guendouzi, Xhaka; Nelson (Martinelli 67), OziL (Willock 78), Pepe (Saka 90+1); Lacazette.
Unused substitutes: Leno, Ceballos, Mavropanos, John-Jule.
Leeds United: Meslier; Ayling (Stevens 79), White, Berardi, Douglas; Phillips; Gotts (Dallas 61), Klich; Alioski (Costa 61), Bamford, Harrison.
Unused substitutes: Cooper, Casilla, Davis, Casey.
Referee: A Taylor (Manchester).