Andoni Iraola said he will instruct Liverpool players to go down in the box in future after Alexander Isak was denied a penalty during Arsenal’s first win at Anfield for 14 years.

Liverpool were beaten by Kai Havertz’s early strike after a poor clearance from the goalkeeper ­Alisson but had two penalty claims dismissed by the referee, Andy Madley. The first, a shirt-pull by the Arsenal defender Jurriën Timber on Isak, prevented the ­Sweden international reaching Bradley Barcola’s cross. The second, a hold by Christos ­Tzolis on Cody Gakpo, was reviewed by the video assistant referee, Stuart Attwell, but rejected.

Isak stood his ground when held by Timber and Iraola claimed that counted against his team. Asked whether Isak should have collapsed in the area, the Liverpool head coach replied: “It’s a shame you ask me this question but, honestly, yes, we have to tell them to go down because they’re not going to call it otherwise.

“And then referees complain why they go down. Because if you don’t go down, you don’t call it. I think Alex is honest. He tries to go for the ball, everyone can see live straight away there is a clear, clear pull.”

Iraola accepted the reasons for ­dismissing the Gakpo penalty claim but believed they were inconsistent with the explanation for not ­awarding the Isak appeal. “I think there are two situations and they are a bit related,” he said.

“The Isak one is a clear penalty. He is going to head the ball in front of the goal and they grab him where ­everyone sees the shirt. The ball just goes in front of Alex and I don’t see the reason why [it isn’t given]. ­

“Probably because he doesn’t dive or he doesn’t go to the floor. It shouldn’t be a reason not to concede a penalty. The Gakpo one, I think it’s a sustained holding but I understand their argument and I think they are right when they say the ball was too long in the air and Cody wouldn’t have arrived to the ball.

“But then you’re basically ­accepting that the first one is a ­penalty, no? You cannot use the ­argument in both ways differently.”

Iraola’s post-match mood ­contrasted starkly with his childhood friend Mikel Arteta. The Arsenal ­manager, who claimed not to have seen the Isak incident, was elated by his team’s reaction to their Carabao Cup exit at Fleetwood in midweek and his first win at Anfield in charge of the Gunners.

Arteta said: “It feels better as a manager [to win at Anfield] because it has been such a long time without this feeling. I am extremely proud, especially given the conditions we arrived to the game.

“The defeat against Fleetwood looks like the end of the world but then you have to pick yourself up. That is the beautiful part of this game. Four days later you have to come to Anfield, and play against this manager, this team who are in a good moment, and so I am so proud of what my team has done.”

Arsenal have now won at four grounds where they did not win when securing the title last season – Anfield, Villa Park, the Stadium of Light and the City Ground.

“This is a mission we didn’t complete for 14 years,” Arteta said. “There were reasons for that. Some were ­psychological, some were related to the quality we showed on the pitch, and some were decisions. We knew we had to nail all of them. We knew we would have to navigate periods where we had to suffer.”

When informed that his team had denied Liverpool a shot on target in a Premier League game for the first time in 16 years, Arteta said: “I didn’t know about that stat but that is incredible. It didn’t feel like that at the time, they are a team that shoots a lot so you have to be good at denying them space and blocking shots. To do that against this team is remarkable, I would say.”