Chelsea failed to capitalise on home advantage as they were held in an entertaining Carling Cup semi-final first leg against Manchester United.
Frank Lampard twice came close, seeing a header flash wide and having a shot cleared off the line by Gabriel Heinze.
But United will feel aggrieved they were not given a first-half penalty after Louis Saha went tumbling.
After the break, Tim Howard saved from Jiri Jarosik, while Carlo Cudicini pushed away Wayne Rooney's header.
The Blues fashioned the better chances, but were unable to break down an excellent visitors' defence.
And United will be glad of the chance to take Chelsea to Old Trafford for the second leg on level terms - although the Blues will be grateful to have prevented Sir Alex Ferguson's side getting an away goal.
An entertaining opening period saw both sides display their attacking intent, but it was Chelsea who came closest, Damien Duff's left-footed strike whistling past the goal.
Saha saw a penalty claim turned down after being sandwiched in the area, and the French striker, starting a match for the first time since 10 November, flashed a free header wide.
Lampard glanced a header inches wide with Howard stranded, and Eidur Gudjohnsen put the ball in the net after Duff's forward pass, although he was comfortably offside.
Chelsea were building up momentum, although United remained a threat and Rooney sent a snap-shot just wide shortly after the half-hour mark.
Tiago saw a shot blocked eight minutes before half time, but it was United who came agonisingly close to scoring with Cudicini diving to push away Rooney's goal-bound header.
Didier Drogba replaced Gudjohnsen at half-time and was involved as Joe Cole almost gave the home side an early second-half lead.
Howard fluffed a clearance with Drogba lurking and Cole's instant volley from the clearance flew just wide.
United were then thankful to Heinze who tracked back superbly to clear off the line after Lampard beat John O'Shea to cleverly fashion a shooting chance before slipping the ball past Howard.
The United keeper then had to adjust sharply to prevent Drogba's deflected shot creeping in as Chelsea put the visitors under early second-half pressure.
It was not all one-way traffic, however, with Rooney seeing a shot blocked and Saha sending one wide.
Yet Chelsea posed the greater threat, and Lampard again came close with a shot which flew narrowly wide.
The Blues could not find a way through, however, and did not help themselves with a succession of poorly-judged dead balls.
And there were anxious faces as Saha got in a free header with 18 minutes remaining, but Cudicini was well placed to save.
Still the chances came and substitute Jarosik forced a superb save from Howard but Chelsea were unable to score for the first time since they were held by Paris St Germain in November.
Chelsea: Cudicini, Paulo Ferreira, Terry, Gallas, Bridge, Lampard, Makelele, Tiago (Kezman 66), Cole (Jarosik 75), Gudjohnsen (Drogba 45), Duff.
Subs Not Used: Cech, Johnson.
Man Utd: Howard, Phil Neville, Silvestre, O'Shea, Heinze, Ronaldo (Smith 90), Fletcher, Djemba-Djemba (Scholes 61), Fortune, Saha, Rooney.
Subs Not Used: Carroll, Miller, Spector.
Booked: Heinze, Ronaldo.
Ref: N Barry (N Lincolnshire).