Arsène Wenger has vowed to make wholesale changes to his side for tomorrow’s Champions League tie against Porto after condemning a performance that he claims left him feeling physically sick. The Arsenal manager was as angry as he has been in 12 years at the club after Saturday’s shock 2-1 home defeat by Hull City and took the highly unusual step of publicly criticising his players.

Wenger stopped short of naming individuals, but left his side in no doubt that they had underperformed after subjecting them to an hour-long dressing-down after the final whistle.

“There will be changes on Tuesday, certainly,” Wenger said. “I will see how many, but there will be changes. There were enough ingredients today to make me physically sick.

“What we delivered today was not good enough and we know that. What was the most disappointing is that we were 1-0 in front and still lost the game, after having struggled in the first half to score.”

Arsenal missed the chance to return to the top of the Barclays Premier League by losing their second match of the season, leading Wenger to question his players’ commitment. “We were not at the level we should have been,” he said. “I believe that’s more down to the mental side than anything technical. If we had had the same level of commitment as Hull, we would have won the game, as the technical advantage is with us.

“I don’t know if they were complacent, it’s difficult to say. Are they subconsciously thinking, ‘It’s OK, we will do it.’ It can happen. But where we are guilty is after a difficult first half, we went 1-0 up and then let it go again.”

Robin van Persie’s place is most under threat after an anonymous performance alongside Emmanuel Adebayor up front, but Wenger also suggested he would look at his established centre-back pairing of William Gallas and Kolo Touré after conceding a soft goal from a set-piece for the third time this season. Fresh from signing a new four-year contract, Johan Djourou is next in line after an outstanding performance in last week’s Carling Cup win over Sheffield United and the Switzerland defender would give Arsenal the height they lack.

“I believe that we have more a size problem than quality in our defending problem,” Wenger said. “Our centre backs are not very tall. I don’t know what we can do. It’s not only centre backs who defend. As a team we are a bit short.

“I do not necessarily think it’s inexperience. We gave them too much room on the first goal and we didn’t clear the ball on the second one, and that’s basically it.

“I don’t know how many games we can afford to lose in the league. What is important now is to recover and prepare for the next one. Can we afford to lose not one more? I don’t know. And what is important now is not how many games we lose in the season, it’s how we respond on Tuesday night.”

Gallas denied accusations of complacency, but conceded that a dramatic improvement is needed if Arsenal are to achieve anything this season. “I don’t think we were complacent and I hope not because if we think like this, we will not go anywhere,” he said. “The players were ready to play a strong game, we were not lucky and we have to work more and try to stay in the fourth position.

“We didn’t know them [Hull] very well, but they showed the character, they showed they can play football. They were very strong and we were not strong enough, so we have to forget that game and think about the next game on Tuesday.”