Noni Madueke made use of the time wisely. With around 20 minutes until kick-off, he saw Bukayo Saka go down the Leeds tunnel injured. A tap on the shoulder and he was in the attacking drills with the other Arsenal starters.
His inclusion in Arsenal's starting XI at Elland Road was only confirmed within 10 minutes of the start, but around 40 minutes later he'd picked up a goal and an assist - his first Premier League goal involvements since swapping Chelsea for Arsenal.
"He was ready," said Mikel Arteta about his stand-in winger. "Because you cannot do that in two minutes.
"The way he prepares, the way he's waiting for an opportunity, and it paid off today because it really impacted him."
Making use of the time has been a theme of Madueke's season so far. The winger was brought in as an option on both right and left flanks for Arsenal - but he's needed to be patient due to the form of Saka and Leandro Trossard in those roles. Opportunities have been limited.
A knee injury early in his Arsenal career did not help his development, while he was then left on the bench for three Premier League games in a row immediately after scoring an impressive brace in the Champions League at Club Brugge.
But after criticism from his own fanbase upon joining the club, with many signing a petition against it, Madueke's output so far for Arsenal has been largely positive.
The last-minute Leeds call-up was not the first time he has had a positive impact at short notice. In the Champions League, there was the quickfire goal off the bench against Bayern Munich.
A closer look at his Premier League numbers look positive too. No player in the Premier League averages more touches in the opposition penalty area than Madueke, who is also ranks highly for dribbles completed, entries into the penalty area and accurate crosses into the box.
Another area Madueke helps out in is through set pieces - he also ranks top in the Premier League for big chances created from set plays per 90.
His goal and assist at Elland Road came through dead ball situations, but he is also superb at forcing them in the first place, winning more corners per 90 minutes than any other player in the top-flight this term.
The corner Madueke scored from was Arsenal's sixth of the game after just 36 minutes - Madueke was responsible for winning three of them. Even Leeds boss Daniel Farke admitted after the game: "Set pieces are a big topic for them. We gave a few too many away."
Madueke's performance at Elland Road saw him be a threat from dead plays but also in the one-on-one duels. It was a Saka-esque performance.
Many felt Madueke was making a mistake going to Arsenal with Saka there. There was also a feeling Chelsea had got a good deal out of his sale, especially with Estevao coming in and taking his spot.
But Madueke has proven to be a more regular threat in the penalty box than the young Brazilian, but also Alejandro Garnacho and Jamie Gittens, other wingers Chelsea invested in over the summer.
Even though Arsenal have played Chelsea twice this season, Madueke has not had a proper chance to face off against his former side. He was a late substitute in the league fixture in November, before going unused in the Carabao Cup semi-final first leg.
For the second leg, all eyes are set to be on Madueke, with Saka a doubt for the game - even though Mikel Arteta has described his 'niggle' as "not too serious".
This is a platform for Madueke to show not just why Arsenal were right to sign him, but why Chelsea may have been foolish to let him go in the first place.
Watch Arsenal vs Chelsea in the Carabao Cup semi-final second leg live on Your Site on Tuesday, kick-off 8pm
