Kennedy, 22 has left Bramall Lane after he was not offered a new deal by the club, ending a 15 year association with the League One side.
He made his Blades debut in the 4-0 defeat at Swansea City in May 2011 with relegation from the Championship already confirmed. Since graduating from the Academy the Barnsley born defender has played just 24 games with his time at the Lane largely hampered by injury.
He leaves United disappointed that he didn't get a fair chance, posting this message on Twitter;
