Shkodran Mustafi could be remaining in La Liga for Valencia, according to Guillem Balague

Arsenal are in danger of missing out on signing Valencia defender Shkodran Mustafi, according to Guillem Balague.

Sky sources reported earlier in August that Mustafi had agreed a move to the Emirates, with negotiations ongoing over the transfer fee, while Arsene Wenger said over the weekend that a deal "will be done" before the transfer deadline.

However, Mustafi's buy-out clause now seems likely to prove a major stumbling block.

I heard Arsene Wenger confirm publicly that Arsenal were in negotiations for Mustafi. That's very rare for him to do so. Perhaps he is trying to apply some pressure on Valencia to sell. Guillem Balague

Balague, Sky Sports' Spanish football expert, said: "The coaching staff at Valencia think Mustafi will not go, and this is the same message being made by Valencia.

"They insist the only way Mustafi will be allowed to leave is if Arsenal trigger his €50m (£43.1m) buy-out clause, which I think everybody will agree is too much money for him.

"Valencia's position is such because they don't think they can find someone to replace him, given the proximity of transfer deadline day. It's a similar stance to the one they have with Barcelona target Paco Alcacer, or at least that's the message they are giving out.

"So, as things stand, neither Mustafi nor Alcacer will be leaving Valencia. I heard Arsene Wenger confirm publicly that Arsenal were in negotiations for Mustafi. That's very rare for him to do so. Perhaps he is trying to apply some pressure on Valencia to sell.

"Valencia have had difficulties with Financial Fair Play, but that has improved recently. They still need to sell one or two players, but they would rather part with the likes of Aderlan Santos or Lucas Orban, sales which they believe would bring the club in line with the regulations.

"So they are not as desperate as some are making them out to be."

Wenger has come under fire for his limited transfer activity and following Saturday's 0-0 draw at Leicester, the Frenchman reassured fans that Arsenal were looking at a "number of players", adding negotiations were "ongoing" on Mustafi.

Arsenal manager Arsene Wenger says he would be willing to spend £300m on the right player if he had the money Arsenal manager Arsene Wenger says he would be willing to spend £300m on the right player if he had the money

Arsenal have had problems at centre-back since Per Mertersacker was ruled out until the New Year, with Gabriel Paulista also struggling to be back in action within the next six weeks.

The Gunners signed 20-year-old Englishman Rob Holding from Bolton, while Poland youngster Krystian Bielik is also being developed as a centre-back.