Sheffield have lost prop forwards Liam Higgins and Leigh Sanders ahead of the 2014 season.
Higgins, 30, has been forced to end his 12-year career due to a serious knee injury.
Speaking of his retirement, Higgins said, “I was really looking forward to the 2014 season with the new start at Owlerton.
“My injury however would leave me out for most, if not all of the 2014 so I decided it’s time to hang up my boots.”
Sanders, 22, is also suffering with a serious injury, although his is not career-ending.
The former Hoyland Vikings and North Derbyshire Chargers man could miss up to two seasons due to a shoulder injury.
Head coach Mark Aston had this to say on Sanders:
“It’s sad that Leigh won’t feature for us this year, he’s a great individual and is a credit to the club.
“He is a prime example of the great work our youth development team is undertaking and our performance pathway.”