The dispute is over Walton's request to play as a defender. Sturrock has used that to keep Walton off the tour.
"He wants to play centre-back and there are other players ahead of him at centre-back," said Luggy.
"Everybody was told that, performance-wise, 22 players were going to get taken [on the tour]: Simon's been left behind.
"Everybody's got a future. If certain players got injured, or anything else, he's available.
"Simon and I have had a good discussion about his whole scenario here and I think it's vitally important that he appreciates the situation."