Spurs entered the finale with a simple task on their hands, beat already-relegated bottom-of-the-table Norwich and secure a return to Champions League football.
Rivals Arsenal needed a Norwich win to have any chance of a top-four finish, but the race was all but over after 32 minutes with the Canaries gifting Spurs a simple 2-0 lead.
Attention then turned to the Premier League's Golden Boot race, with Son battling Liverpool's Mohamed Salah for the honour and heading into the game one goal behind.
Shortly after Tim Krul rewarded Harry Kane with a tap-in, the goalkeeper atoned for his error with a stunning point-blank stop on Spurs' no.7, and Kulusevski then attempted to get his teammate on the score sheet.
"Two minutes before the goal there was a weird situation, I was free with the goalkeeper and a lot of things went down," he said on the DÅ ÄR VI IGÅNG podcast, wearing an Argentina shirt of teammate Cristian Romero.
"A guy tackled me, I'm alone with the keeper, I was thinking 'should I lay down, he's going to get sent off'.
"But I was like 'No I have to score of course' so their keeper comes out and then he hesitates so I realise that I'm going to get there first.
"So I run past him, I have an empty goal in front of me, I was like 'Man, this is awkward'. I don't really like having an open goal.
"Because you have too much time to think?" asked the interviewer. "Exactly!" replied the Swede.
"And the fans are right next to me they are shouting 'Gimme, Gimme' right next to me.
"I'm like 'take a deep breath, take your time Dejan you have an empty goal'. I'm staring at it, you know, it's definitely empty. But I take one more touch, then I think 'now maybe it's finally time to shoot'.
"But then I see Son, I see my teammate Son, he's like 'pass me the ball' he needs one more goal to win the Golden Boot and we all said before the game that we need to pass to Son, you know Son has to win the Golden Boot.
"So I'm like 'Dejan forget about the goal, you have to assist Son' so I pass the ball, and when I pass the ball I get stuck in the ground, so it becomes a bad touch and the ball just rolls slowly towards goal and they clear the ball on the goalline."
Kulusevski clearly made the wrong call after a stunning turn left two Norwich defenders for dead, creating the golden chance.
However, The Tottenham winger soon made amends though, curling a beauty into the far corner to silence the Norwich crowd in a final day drubbing.
"So I just stand there after thinking 'Bro, Dejan, what the f*** are you doing?'" he said. "I'm thinking 'You are the biggest idiot' and I felt so ashamed.
"I got so frustrated and was like 'Give me the ball again' two minutes later I got the ball again and then I don't think at all I just put the ball in the top corner."
With the score 3-0 and the game put to bed, Son was then able to score his 22nd and 23rd goals of the season to lead Salah, only for the Egyptian to net late against Wolves and share the honours.