Arsenal manager Arsene Wenger feels any weakness will be punished in the race for the Barclays Premier League title this season.
The Gunners made the most of slip-ups by Chelsea and Manchester United with a hard-fought 2-0 victory at West Ham on Sunday to keep pace with leaders Liverpool, whom they trail by four points.
"One week ago everyone made Chelsea super-favourites, now it is Liverpool. Things change very quickly, which is why it makes it very interesting," said Wenger.
Arsenal came through a stern test with flying colours to beat Fenerbahce 5-2 away in the Champions League on Tuesday and they certainly had to dig deep for their win at Upton Park.
In the end, an own goal by Julien Faubert from substitute Emmanuel Adebayor's shot broke the deadlock, before the Togo striker wrapped things up in stoppage time.
Wenger feels the battle for supremacy this season will be tight, with little further margin for error - his men having already lost twice.
"We were very close last year and with 83 points, many times you would have been champions," he said. "However, Manchester United had a fantastic second half of the season, we dropped a little bit of our quality and that is it - I still feel any weakness will be punished."
Hammers manager Gianfranco Zola maintains his side - who on another day could well have had a penalty for handball against Abou Diaby just before Arsenal's second - are heading in the right direction.
"I know it might look crazy, but I am not worried at all, because we are going to get through this," he said.
"It would be easy for me to have a go at them, but the players' commitment is fantastic and their attitude is perfect. They were doing everything I asked them to on the pitch, so I can have no complaints."