Sunderland have been sent an eye-opening warning about manager target Will Still. Sunderland were handed a huge potential boost in their managerial hunt when long-term target Still, 31, left French Ligue 1 side Reims at the start of May. Still was wanted by Sunderland after the club sacked Tony Mowbray, and he reportedly spoke to club officials before Michael Beale was brought in. Reims’ hefty compensation fee for Still was thought to be a deterrent for the Black Cats, but Still is now a free agent. Sunderland owner Kyril Louis-Dreyfus is yet to pull the trigger on a move for Still but it’s th…