Derby County failed to make up ground on leaders Norwich City as Steve McClaren's men were held to a goalless draw by Millwall.
Jamie Ward looked to fire the Rams into an early lead as he had two chances inside the opening minutes, only to be kept out by the away side's backline.
Millwall were limited in attack early on, but slowly began to create opportunities as both Lee Gregory and Matthew Briggs came close to getting on the scoresheet midway through the first period.
Ward then produced a fizzing strike that looked to be heading for the top corner of the Lions' net, but for the intervention of keeper David Forde.
In first-half stoppage time Aidan O'Brien had his effort blocked as Ian Holloway's men went in at the break with cause for optimism.
However, their defence was almost breached early in the second period as Jordon Ibe and John Eustace both missed chances to give the Rams the lead.
Substitute Jeff Hendrick, back from a lengthy injury lay off, nearly netted on his return when he met Chris Martin's cross, only for his effort to be repelled by a Millwall rearguard desperate to keep a clean sheet.
The visitors offered their own threat in attack with Scott McDonald missing two late shots at goal.
Johnny Russell was also frustrated with his stoppage-time effort as Derby missed the opportunity to move to the top of the Championship, remaining in fourth place.
