Mike Whitlow, who decided not to renew his Bolton Wanderers contract at the Reebok Stadium. The centre-back played a part as a trialist in the 9-0 demolition of Frechville and signed for the Blades today.
Another trailist, Andy Parkinson from Tranmere Rovers has agreed to sign for the club, both players join a free.
Speaking about 24-year-old former Tranmere winger Parkinson, Warnock told the club's official website (www.sufc.co.uk): "Parky is someone we've looked at over the years, as we did when we were chasing Jack Lester.
"I do believe we have got a player at the right age, who has put football before financial gain. He is a good addition to the squad, very quick and he can play all along the front line."
Experienced defender Whitlow, 35, has joined the Blades after rejecting a new contract with Bolton.
Warnock added: "We are delighted to get Mike on board - I feel his experience in central defence and at full-back will be an asset to the squad."