Steve Evans's men saw an early penalty appeal turned down when Mirco Antenucci went down inside the box, only for the referee to wave away appeals on the grounds that Lee Peltier had made minimal contact.
Leeds were just about edging things in the opening 15 minutes, but the visitors created an opening through Alex Revell which the forward flashed over the bar on the half-volley.
It took until the half-hour mark before the fans had a chance to truly get excited about anything, though, with Stuart Dallas bursting forward and firing one narrowly wide from 25 yards out.
Dallas and the returning Alex Mowatt themselves saw half-chances come and go before the interval, as the Whites upped the pressure in search of a way through, but Marshall remained strong to keep out the former's drive.
The opening 45 minutes eventually came to a goalless conclusion, but only after Chris Wood headed Bellusci's deep cross wide of goal to see Cardiff's run without conceding extend into another half.