Xhaka was seen as a statement signing by Sunderland from Bayer Leverkusen last summer, and Regis Le Bris' decision to instantly make him captain has paid dividends.
The Swiss international has been the beating heart of the Black Cats' surprise European push, assisting six times and scoring once in 32 Premier League appearances.
Combining supreme technical qualities with indispensable leadership, Xhaka has become a fan favourite in the North East, and supporters want him to stay for as long as possible.
But since he turns 34 later on this year, the former Arsenal man could seek a new challenge, and according to Turkish outlet Fotomac, Xhaka is "open" to joining Besiktas.
The Turkish giants are determined to strengthen their midfield, while Besiktas fans are "positively inclined" towards the 33-year-old.
Sunderland will hope that speculation over his exit subsides in the coming weeks and months, as he's undoubtedly a key cog in their well-oiled machine.