Former Aston Villa boss Paul Lambert has been impressed by Moussa Diaby this season.
Lambert, formerly of Borussia Dortmund, is well aware of the winger's qualities.
I just think they have good players there I really do," said Lambert.
I think he's [Unai Emery] bought really wisely. I saw Diaby play a long time ago at Leverkusen because I follow German football pretty well.
"I always wondered why he had never moved to a really big, big club."