By Chris Harris

Arsenal's defence can be their foundation for success this season, according to Per Mertesacker.

The Germany international returned to the heart of Arsène Wenger's back four on Saturday and helped guide Arsenal to a 3-1 win over West Ham United.

Olivier Giroud, Theo Walcott and Santi Cazorla got the goals but Mertesacker and his fellow defenders dealt expertly with Andy Carroll as the home side exerted pressure.

"We could feel in the air it was going to be a tough game," said Mertesacker. "We had to fight a lot, especially in the second half when the crowd became West Ham they had a good advantage.

"But we came back into the game on the counter-attack and afterwards we played well, especially defensively. We won more and more headers which was vital.

"It [our defending] can be the difference, it is crucial for us that the defence is winning more games. We just try to keep that in our mind the whole year."

Arsenal's win at Upton Park was all the more impressive after they fell behind to Mohamed Diame's fine first-half finish.

"What can you do about their goal? Sometimes that happens," said Mertesacker. "We have not conceded a lot of goals during games this year and most have been from set-pieces. We just need to keep concentrating on our defensive level.

"We needed to win to bounce back after the defeat against Chelsea. It's always good to win in front of an international break. We have good confidence and showed that especially when it was tough in the second half.

"West Ham had a few chances but we didn't let ourselves down. We kept our chins up and we have unbelievable quality on the bench which made the difference."

Copyright 2014 The Arsenal Football Club plc. Permission to use quotations from this article is granted subject to appropriate credit being given to www.arsenal.com as the source 7 Oct 2012