Nathan Baker is back in training - but he won't be fit for the Southampton game on Saturday.Tim Sherwood confirmed that the centre-half returned to the fields of Bodymoor Heath this week.Baker has been out since coming off in the FA Cup semi-final against Liverpool.The 24-year-old has missed matches against Manchester City, Everton and West Ham with a knee injury.However, the Saints clash will come too soon for the combative stopper.But he will be assessed ahead of the Burnley and Arsenal encounters.He said: "Nathan hasn't trained for too many days."It will be too early for him this weekend."Sherwood also confirmed that Libor Kozak joins Chris Herd and Ciaran Clark on the sidelines.Striker Kozak has injured his back.It is not serious - just a "wear and tear" injury.He, too, will be monitored in the closing weeks of the season.Sherwood also revealed that Gary Gardner and Callum Robinson have been training with the first team this week.