On a night when Liverpool celebrated the goalscoring arrival of their record signing Alexander Isak, a moment of "stupidity" proved costly for their other in-form forward.Hugo Ekitike scored the winner in Tuesday's 2-1 victory against Southampton as the Reds progressed to the fourth round of the Carabao Cup.But, caught up in the moment of his 85th-minute goal, striker Ekitike removed his shirt and held it up to the Liverpool fans in celebration.He most likely knew he would get booked and was happy it was a price worth paying, but what he had seemingly forgotten is he had already been shown a yellow card.The sending-off means he will be suspended for Saturday's Premier League game at Crystal Palace - not ideal when the player he is potentially in a battle for a starting spot with is returning to full fitness.Ekitike went on social media on Tuesday night to apologise, saying: "I was so excited to help the team achieve another victory here in our home for my first Carabao Cup match. "The emotion got the better of me. My apologies to all the Red family. Thanks to the fans who always support us and to my team-mates for this victory!"But, speaking just after the game, his manager Arne Slot was left bemused."It is not [stupid] because it was his second [yellow] - it's stupid even if you haven't had a yellow card yet," he said. "Maybe I'm a bit old-fashioned but I did score a few goals - not at his level, but I did - and if I went past three players and put it in the top corner then maybe you can say: 'This is all about me.'"But if I scored a goal like he did tonight, I would turn to Chiesa and say: 'It's about you Federico - great assist, great run and I didn't have to do a lot.' Maybe that's me being old-school. "It was stupid, not smart in every sense. The good thing is that his team-mates helped him to get the win over the line, but the thing is he is now suspended for Saturday and that is far from ideal."Liverpool signed Ekitike for £69m in July from Eintracht Frankfurt and he has started the season in excellent form.Leading the line while the Reds completed the deal for Isak then took their time working the Sweden forward up to full fitness, he has scored three goals in five Premier League games and provided one assist. That has helped Liverpool win every game they have played since their Community Shield defeat by Crystal Palace on 10 August, and underlines his importance to the team, regardless of his unnecessary dismissal on Tuesday.Indeed, both cards he picked up were needless. Replacing Isak for the start of the second half, he was booked soon after when he threw the ball in the air after being penalised for a foul.Former Premier League striker Chris Sutton said on BBC Radio 5 Live that Ekitike had shown "sheer stupidity" to be sent off for taking his shirt off.He added: "He's been such an important player for Liverpool so far this season - what a start to his Liverpool career, important goal [against Southampton] - but that's not great for Arne Slot if he's sitting out the game at the weekend."The main thing Ekitike is likely to take from this is an important learning experience."I'd be very surprised if he does it again," added Slot."He probably forgot he got a yellow. He's young and he will learn from it. I'm sure he won't do it again."