Son Heung-min described Tottenham’s 4-2 Premier League defeat at Brighton on Thursday night as a “big wake-up call” after a performance that was “nowhere near the level” required.

Spurs lacked sharpness – a consequence, surely, of being stretched by injuries – and were ripped apart by a rampant Brighton who took a 4-0 lead, the outstanding João Pedro scoring two of them from the penalty spot. Son’s team rallied in the last 10 minutes, scoring twice, and they pushed hard during nine additional minutes when they almost scored a third, advertising the wildest of comebacks.

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But Son, who will depart in early January for Asian Cup duty with South Korea, made it clear that the response was too little, too late.

“It is a very disappointing performance,” the captain said. “This is not how we’ve approached the season. This performance was nowhere near the level we want to play at.

“We have to talk about the first half and the early parts of the second half rather than the end. We know we have to play like that from minute one. Every team is strong in the Premier League and if we’re not playing like the last 15 minutes in every game we’re going to struggle. This has to be a big wake-up call. The first half was not our game and not us. We have to take a big, big lesson.”

Ange Postecoglou was upset at the award of Pedro’s first penalty for 2-0; it was given after advice from the VAR that Dejan Kulusevski had pulled Danny Welbeck’s shirt. In the 81st minute, the officials only booked the Brighton captain, Lewis Dunk, for an X-rated tackle on Kulusevski in the build-up to Spurs’s first goal, scored by the substitute Alejo Véliz.

“It [the first penalty] was obviously clear and obvious because it only took him [the referee, Jarred Gillett] three minutes to see it on the screen,” Postecoglou said. “VAR picked up everything today except the one tackle which nearly cost me another player.”

Roberto De Zerbi, whose resources have also been severely depleted by injuries, said it was “the best way to finish the year”. The manager called Pedro the best player on the pitch and said: “I hope in the next year to work with him but I think it will be very tough.”