Butler, 30 will be a free agent this summer after turning down a new contract with League One rivals Walsall but the Blades who are considered favourites to snap up the defender may face competition from hometown Doncaster Rovers and former club Scunthorpe United.
The Doncaster born centre-half still lives in the South Yorkshire area and it is teh commute to the Midlands that Saddlers boss Dean Smith is the reason behind his wanted exit; “At his age it can be hard work when you have young kids and have to come down to train,” Smith said. “I think we have had the best three-and-a-half years out of him. He has been brilliant. Andy was always honest with me from the start,” Smith added. “And at the end of the season he told me that he would have a really tough decision to make.”