The Ligue 1 champions have failed to agree a fee for the 22-year-old with the principality based side. Their £12.9 million offer was well short of the £18 million that their rivals wanted for the France international, and is has spelt the end of their interest in the player after a slightly improved bid was also rejected.
This has left the way clear for the Premier League duo to make a move, although the pair do already have serviceable left-backs. The Red Devils have Luke Shaw, who was brought in for big money just two seasons ago, and are unlikely to bring in another for the position as Marcos Rojo, Daley Blind, and Ashley Young can also play in the position.
Meanwhile, the Gunners have Nacho Monreal, who has become a regular since winning his place ahead of Kieran Gibbs last season. The England international is still with the club, so they would surely sell before bringing in another full-back.