Millwall and Derby County will have to play it again on Tuesday 12th January to decide which team takes their place in the FA Cup fourth round following an absorbing third round encounter at The Den.
A possible upset looked to be on the cards when Lewis Grabban headed The Lions into a 49th-minute lead, but less than 120 seconds later parity was restored for Nigel Clough's Championship outfit when Kris Commons drilled home a leveller.
Kenny Jackett's side will most definitely be left wondering what might have been after proving more than a match for their higher league opponents for much of this game.
Fielding a 4-4-2 formation with Grabban partnering Steve Morison up front, Millwall started brightly and asked questions of a Rams rearguard that at times looked quite cumbersome.
On 12 minutes Grabban fed Marc Laird and his smart reverse pass picked out Jack Smith, who shimmied past two defenders before firing into the side netting with the first clear chance of the game.
Seconds later Rob Hulse broke clear of the home defence, but thankfully managed to screw his angled effort wide of goal with only keeper David Forde to beat as Derby briefly threatened.
Millwall responded positively with roving right-back Smith thumping another effort narrowly wide and a couple of Chris Hackett corners caused consternation amongst the visiting ranks.
But the clearest opportunity of the half fell to Derby on the stroke of half-time when Commons' right-wing cross deflected off Jimmy Abdou and needed the intervention of skipper Paul Robinson to head off the line for a corner to avert the danger.
Rams boss Nigel Clough introduced loan signing Lee Johnson for the ineffective Lee Hendrie at the break, but the second half was barely four minutes old when Millwall took the lead.
Smith's powerful run began the move before he slipped the ball to Hackett on the right. He in turn despatched a perfectly weighted cross into the path of Grabban who produced a perfect header that left keeper Stephen Bywater grasping at thin air.
But the celebrations were still in full swing when The Lions were caught napping from a Dean Moxey throw into the danger zone just 110 seconds later. The ball fell perfectly for Commons, who made no mistake with a low drive that flashed into the bottom corner past a static David Forde.
Back came Jackett's men with renewed purpose and a stinging Dave Martin drive after Robinson's deep free-kick had only been half-cleared flashed inches wide of the post.
At the other end a quick, slick counter attack saw Derby's Miles Addison surge forward from deep inside his own half, slip the ball to Chris Porter who in turn picked out Rob Hulse but he fired wide from 10 yards when it seemed easier to score.
The game had really opened up now and it was Millwall's turn to go close; Grabban found Laird who produced a delightful floated cross that picked out the unmarked Martin 10 yards out, but his header glanced wide.
Steve Morison thought that he had put The Lions ahead with 14 minutes remaining, powering a header that appeared destined for the back of the net until Moxey booted the ball off the line, with Morison's fierce follow-up shot also blocked.
Jackett brought on Jason Price and Danny Schofield in a last-ditch throw of the dice to conjure up a late winner.
Morison's shot on the turn flew wide and Price was crowded out as he prepared to pull the trigger from a good position, but Millwall just could not find a way through for a second killer goal setting up a third round replay in 10 days time.
Millwall: Forde, Smith, Robinson, Craig, Frampton, Hackett, Abdou, Laird, Martin (Schofield, 87mins), Morison, Grabban (Price 87mins). Subs not used: Sullivan, Dunne, Ward, Fuseini, Grimes.
Bookings: Smith (53mins) Morison (66mins)
Scorer: Grabban (49mins)
Derby County: Bywater, Connolly, Addison, Buxton, Moxey, Hendrie (Johnson, 46mins), Green, Pearson, Commons (Teale, 92mins), Hulse (Davies, 76mins), Porter. Subs not used: Deeney, Pringle, Mendy, Ball.
Booking: Hulse (26mins)
Scorer: Commons (51mins)
Referee: J. Linington
Att: 10,531 (away 1,387)