Arsenal manager Arsene Wenger did not sign Shkodran Mustafi before the start of the season because he was relying on Per Mertesacker. The 24-year-old German joined the Gunners from Valencia shortly before the summer transfer window closed – and Wenger has revealed the role Mertesacker's long-term knee injury played in Mustafi's £35m ($42.8m) transfer.

Arsenal fans bemoaned their inability to sign an experienced centre-back before their opening game of the season, when they were defeated 4-3 against Liverpool at the Emirates. But, speaking during the club's annual general meeting, Wenger has explained the rationale behind his transfer moves.

"Why did I not buy a centre-half before the start of the season? Mertesacker was injured very early," the Arsenal boss said of his captain, according to The Mirror.

Wenger revealed Arsenal agreed a deal with Mustafi's agent during their summer tour of the US in July, but said it took a long while to convince Valencia to sell the highly-rated defender.

"We started negotiating, we met with [chief executive] Ivan Gazidis in the States [and] the agent of Mustafi and agreed the deal. But it took long to get over the line as Valencia were reluctant to sell," he shared.

Wenger stressed, too, that Mustafi was injured during Valencia's pre-season campaign and would, therefore, have been unavailable for the Liverpool game. "We also took longer because in pre-season he was injured and he couldn't have played against Liverpool," Wenger said of Arsenal's summer transfer business.

"When he came he had had just 45 minutes of competition. We needed him to push too and that is sometimes a slow process as it is not only us that can decide whether he signs. With centre-backs, if you look at the investments made all over the country it is a difficult subject as a lot of clubs invested a lot of money and it is difficult to find the quality to strengthen your squad."