The Eagles will start as favourites on Sunday, but Aston is refusing to write off a Batley Bulldogs team coached by his former mentor John Kear.
Kear was in charge of Sheffield when they won the Challenge Cup in 1998 and Aston claimed the Lance Todd Trophy.
Aston said: “Their result (last week against Featherstone) shows the character of that group of people, and the desire and will they have.
“They were losing 18-0, so to pull that back against Featherstone at their place is a pretty remarkable effort.
“I’m really pleased for John and for Batley – they’ve worked hard for the last so many years without a lot of credit.”
Bulldogs coach Kear must select a squad without Jacob Fairbank, who suffered a shoulder injury last week.
Kear said: “We have a thing about ‘Bulldog spirit’ and we showed that last week.”
He added: “Facing Sheffield, you couldn’t have written it better for me. I’m really looking forward to it.
“We’ll turn up and have a go. All the lads will put their hand up and work hard; they’re a good group of people.”