The 23-year-old is on the transfer list at Leeds after failing to agree a new deal at Elland Road and has attracted attention from Bolton and Stoke.
Heading off: Wigan, Stoke and Bolton are all keen on Johnson
Johnson's contract expires at the end of the season and Leeds are prepared to sell him in January rather than risk losing him for nothing at the end of the season.
Meanwhile, Leeds have taken Jamaica international Jason Morrison on trial.
On the look out: Leeds boss Grayson has handed a trial to Jamaica international Morrison
The 26-year-old midfielder played 70 minutes of a behind-closed-doors friendly with Newcastle on Monday.
Manager Simon Grayson also ran the rule over 17-year-old Everton academy starlet Zac Thompson in the friendly, which his side won 4-1.
Johnson tells Bates he is committed to Leeds as war of words intensifiesStoke and Bolton on alert after Leeds stick Johnson on the transfer listWIGAN ATHLETIC FC