If combining physical and mental training, timing is not critical if adequate sleep is obtained that night.

“if you are doing the maximum amount of physical training that you can do according to your schedule preventing injury and all those sorts of important constraints and you're going to add mental training and imagery it doesn't really matter when you do it you could do it immediately after your physical training you could do it on a separate day but you do want to place it at a time in which you can try and get good sleep that night”