The 33-year-old confirmed his retirement in the aftermath of the final game of the 2019 season at Swinton, following two spells with Eagles and stints with Dewsbury and Batley.
Aston confirmed it was a decision he respected but did take him by surprise as he now looks to plug the gap left by one of his most trusted deputies in the dressing room.
Aston may now be slightly on the back foot as he looks for a half-back partner for Anthony Thackeray, but confirmed he is not perturbed by the situation with plenty of options in house.
“Potentially we'll have to now look at filling that spot,” Aston informed The Star.
“We have other options within the squad though. The key is we have plenty of players here who can operate in different roles. There's no massive panic, but obviously we are looking.”
Aston wanted six new faces for 2020, but may now look at tweaking his cohort to bolster his options following Walker’s departure.
He knows replacing Walker on and off the field will be tough, but he still yet may look at home for a replacement.
He added: “Where do you get half-backs from? They aren't the easiest to pick up. That's the big thing for us. We are looking for one, it isn't easy, but we are not panicking over the situation because we have players here already who can play that role quite comfortably.”