The 28-year-old, who currently represents Chesterfield, last played for the Blades in 2012 before he was found guilty of raping a 19-year-old women in a hotel room in 2011.
Evans was sentenced to five years in prison after being found guilty of the offence, but the conviction was quashed and, following a re-trial last October, the Welshman was acquitted.
The centre-forward joined Chesterfield last summer following his release from prison, and has netted seven times in 29 appearances for the already-relegated League One outfit this season.
According to BBC Sport, soon-to-be Championship side Sheffield United and Chesterfield have agreed a deal of £500,000 for Evans, who scored 42 goals in 103 league appearances at Bramall Lane between 2009 and 2012 following his release from Manchester City.
Evans has not played for Chesterfield since March.