A huge let-off for Donegal.

Charlie McMorrow races through on goal and looks set to put the game beyond doubt, but his curling effort crashes back off the post and away to safety.

Dublin then make another change, with Con O'Callaghan's afternoon coming to an end as Tim Deering is introduced.

Donegal remain alive, but time is running out.

Seán Guiden is proving to be the difference-maker in extra-time.

The substitute bursts forward once more and confidently splits the posts from close range for his third score since being introduced.

Three minutes remain in the opening period of extra-time and Dublin's lead is now at five points.

It has been all Dublin in this opening period of extra-time.

Seán Guiden continues his superb impact off the bench, curling over a brilliant two-pointer from the right-hand side to stretch the hosts' advantage.

Donegal have yet to trouble the scoreboard in extra-time and the Dubs now lead by four points.

Dublin are beginning to dictate the tempo, working the ball patiently as Donegal are forced to chase the game.

The hosts almost extend their lead further through Ross McGarry, but his effort strikes the upright and rebounds wide after four minutes of extra-time.

Ger Brennan also makes a late change as Sean Bugler replaces Lee Gannon.

The Dubs have not been deterred by the loss of two players.

Ross McGarry continues his impressive cameo from the bench with another point before Seán Guiden follows up moments later to double Dublin's advantage.

An ideal start to extra-time for Ger Brennan's side despite being reduced to 13 men.

We're back under way at Croke Park after a breathtaking finish to normal time.

But there has been a major twist before the throw-in.

Referee Martin McNally has issued four black cards following the melee at the end of normal time - two for each side. Donegal will be without Michael Murphy and Jason McGee, while Dublin have lost Niall Scully and Theo Clancy.

That is a huge development, particularly for Donegal with Murphy forced off after his dramatic late two-point equaliser.

The drama continues in this extraordinary All-Ireland eliminator.

John McGovern
BBC Sport NI contributor at Croke Park

What a remarkable finish we have just witnessed at Croke Park.

It looked all over when Paddy Small's late goal put Dublin firmly in control and Lee Gannon followed up with a point to leave Donegal staring at elimination.

But Jim McGuinness' side refused to go quietly.

Michael Langan kept their hopes alive with a late point before Michael Murphy produced a moment of pure brilliance, converting a pressure-laden two-point free after the hooter had sounded to force extra-time and send the stadium into raptures.

Tempers then spilled over, with players from both sides involved in a melee before referee Martin McNally restored order.

The dust has barely settled, and there may yet be further consequences from the aftermath of Murphy's dramatic equaliser.

After one of the most dramatic finishes of this year's championship, we now have another 20 minutes to separate these two sides.

What a Round Three eliminator this has been.

The drama continues at Croke Park!

With the hooter already sounded, Donegal are awarded one final opportunity and Michael Murphy steps forward from beyond the two-point arc with the season on the line.

The veteran holds his nerve and lands a magnificent two-pointer to level the contest and send the Donegal supporters into raptures.

Tempers have flared in the aftermath, with players from both sides converging as referee Martin McNally attempts to restore order.

We are heading to extra-time.

Hearts were in mouths around Croke Park for a moment.

Michael Langan lets fly with a fierce effort that appears destined for the net, but the ball just clears the crossbar instead.

Donegal get only a point from the attack when they desperately needed more, leaving Dublin still two points clear in the closing moments.

Dublin can almost taste a place in the quarter-finals now.

The Dubs work the ball patiently down the left before Lee Gannon is picked out in space in the centre and calmly fists over the bar.

That extends the lead to three points and leaves Donegal with a mountain to climb.

Less than a minute remains for Jim McGuinness' side to find a response.

A huge moment in this enthralling contest.

Con O'Callaghan bursts through the heart of the Donegal defence before producing a perfectly weighted pass to Paddy Small on the right.

Small takes it in stride and drills a low finish into the far corner of the net.

With just three minutes remaining, Dublin have turned the game on its head and lead by two points.

What a game we are witnessing at Croke Park.

What a response from Dublin.

Colm Basquel produces a superb two-point score from play down the right flank to haul the Dubs level and ignite the crowd at Croke Park.

But Donegal refuse to yield.

Jason McGee responds almost immediately with his third point of the afternoon, nudging the Tir Chonaill men back in front.

Five minutes remain and the margin is as slender as it gets.

A breakthrough at last.

Jason McGee ends the scoring drought with a composed point to nudge Donegal back in front with a brilliant two-point effort, prompting huge cheers from the travelling support inside Croke Park.

The noise levels rise even further moments later as Ciaran Thompson is introduced in place of Conor O'Donnell, marking his long-awaited return after his lengthy spell on the sidelines.

Donegal are finding scores hard to come by as well.

Conor O'Donnell has the latest opportunity to edge the Tir Chonaill men back in front, but his effort drifts wide of the target.

Neither side has been able to land the decisive blow as this tense contest remains finely poised entering the closing stages.

Another chance goes begging for Dublin.

This time Niall Scully is unable to find the target as the hosts continue to probe for a score that would put them in front.

Donegal successfully claim the resulting kick-out as we enter the final 10 minutes of this absorbing contest at Croke Park.

Ross McGarry is making quite the impact off the bench.

The substitute is on hand again to split the posts and draw Dublin level before Theo Clancy brilliantly claims the ensuing kick-out to keep the pressure on.

The Dubs sense an opportunity, but Lee Gannon cannot capitalise, dragging his effort wide from a promising position.

A huge let-off for Donegal.

Donegal hit back in emphatic fashion.

Shane O'Donnell takes aim from beyond the two-point arc and lands a superb effort to restore the visitors' advantage.

But Dublin respond almost immediately through substitute Ross McGarry, who makes an instant impact by splitting the posts just moments after his introduction.

We're level once again at Croke Park.

Peadar Ó Cofaigh Byrne bursts into space and looks set to pull the trigger, but his effort is blocked behind for a 45.

Con O'Callaghan steps up and calmly converts the resulting kick, bringing the sides level with just over 20 minutes remaining.

Dublin then make a change, with Ross McGarry replacing Cormac Costello.

Ryan McHugh's effort drifts wide as Donegal miss the chance to extend their lead.

Dublin are quick to build from the resulting kick-out and patiently work the ball around the Donegal defensive arc, probing for an opening as the visitors hold firm.

The tension continues to rise with every attack as 20 minutes remain.

Dublin claim yet another Donegal kick-out and the urgency around Croke Park is beginning to build.

The ball eventually falls to Cormac Costello with a chance to level matters, but under pressure the Dublin forward pulls his effort wide.