Arsenal are scrambling to make a new centre-half signing.
The Daily Mail says Shkodran Mustafi remains the club's primary target, but the move has stalled due to Valencia insisting Arsenal must match the Germany international's £42million release clause.
Talks are ongoing, but time is running out with the Gunners exploring a host of fall-back options.
The club have a long-term interest in Manchester United defender Phil Jones having tried to sign him from Blackburn in 2011.
United insist Jones is not for sale, but the Gunners could launch another move if the situation were to change.