Danny Wilson has added to his striking options ahead of the new season with the signing of striker Chris Porter on an initial two-year contract.
Porter, 27, was a free agent after being released by Derby County at the end of last season, with his last goals coming against the Blades at Bramall Lane for the Rams second string, as they clinched the totesport.com league title in May.
The Wigan-born marksman also started for County in their 1-0 victory against United in the Championship in February.
Boss Wilson commented: "It is difficult trying to find strikers who will score goals at this level and if you look at Chris's career, possibly his most productive time was when he was at Oldham in this division where he scored a lot of goals. We know what he is about and he is very hungry after overcoming some injury problems.