Lee Williamson struck a controversial stoppage-time equaliser for Sheffield United to prevent his patched-up side crashing to a third straight defeat and deny Derby a rare away win in the Coca-Cola Championship this season.

Blades midfielder Williamson slammed home a cross from Mark Yeates on the edge of the penalty area in the 91st minute after referee Graham Salisbury had failed to see Derby manager Nigel Clough's attempts to send on substitute Russell Anderson.

Robbie Savage appeared to have secured Derby back-to-back league wins after last week's home success over Nottingham Forest, the Rams midfielder sweeping home a low shot from outside the penalty area in the 17th minute.

But Clough's side, who started the day in 18th place and only six points above the relegation zone, were denied by Williamson after dominating against a Blades outfit depleted by injuries.

United manager Kevin Blackwell was able to field only three recognised defenders, with skipper Chris Morgan the latest to succumb to the injury curse that has blighted the Blades all season.

Morgan tore a rib muscle in the midweek defeat at Watford, so new signing Nyron Nosworthy partnered on-loan Toni Kallio in central defence on his home debut, while midfielder Nick Montgomery was deployed as an emergency right-back.

Derby midfielder Michael Tonge, a Blades player for eight years, made his Rams debut after joining on loan from Stoke until the end of the season and he was the only change from the side that beat Forest.

Paul Green was guilty of a glaring miss for Derby in the sixth minute when he dragged his close-range shot wide, but the visitors took the lead in the 17th minute before the Blades had mustered a shot on goal.

Savage found himself in space 25 yards from goal and had time enough to unleash a low right-footed shot beyond home goalkeeper Mark Bunn into the bottom corner.

Kris Commons then forced Bunn into a fine save with a low shot and Tonge's angled drive was blocked by Jordan Stewart as Derby assumed complete control.

Commons brought the best out of Bunn again after cutting in from the right and firing in a shot from 12 yards just before the break.

Mark Yeates, also making his full debut for the Blades, arrowed a left-footed shot past Derby goalkeeper Stephen Bywater's left-hand post in the 53rd minute, but Derby were still enjoying the lion's share of the ball without creating clear-cut chances.

Yeates curled a free-kick over the crossbar and Derby defender Jake Buxton did well to block a shot from Ched Evans before United were dealt another major injury blow, with keeper Bunn forced off injured and replaced by veteran Ian Bennett.

The home side then missed a golden chance to draw level. Bywater kept out Stewart's 25-yard piledriver at full stretch and when the rebound fell to Henri Camara, the Blades substitute's shot rebounded back off the Derby keeper.

Buxton headed a corner from Yeates just past his own post and Stewart lashed another long-range effort, this time on the volley, just wide.

But just as Derby appeared to comfortably held on, Williamson pounced on Yeates' ball in to fire home into the bottom corner.

Teams:

Sheff Utd Bunn (Bennett 68), Montgomery, Nosworthy, Kallio,Stewart, Yeates, Williamson, Quinn, Cresswell,Evans (Camara 69), Henderson (Ward 63).

Subs Not Used: France, Little, Geary, Fortune.

Booked: Williamson, Kallio.

Goals: Williamson 90.

Derby Bywater, Hunt, Barker, Buxton, McEveley, Tonge, Green,Savage, Pearson (Teale 72), Commons (Porter 83),Hulse (Anderson 90).

Subs Not Used: Deeney, Pringle, Moxey, Vidal.

Goals: Savage 17.

Att: 25,300

Ref: Graham Salisbury (Lancashire).