This could be huge.

Not fully fit, Galway's superstar forward Shane Walsh is replaced by Daniel O'Flaherty.

On the field of play, Oisin Gallen misses a straightforward fre.

Philly McMahon
Eight-time All-Ireland winner with Dublin on BBC Sport

I still can't get my head around why Galway are not pressing Donegal's kick-outs.

Like, McGee has gone off. Why are they not pressing?

Michael Langan levels things up, as Donegal's talisman Paddy McBrearty heads for the bench, replaced by Niall O'Donnell. Jason McGee is replaced by Hugh McFadden. Johnny Heaney is on for Cein Darcy for Galway.

Philly McMahon
Eight-time All-Ireland winner with Dublin on BBC Sport

Again, like we seen from the score previously where the movement off the shoulder, there's two or three players moving off the one play.

That's what's going to be needed to break down that mass defence.

John Maher grabs the first score in 14 minutes, fisting over the bar. With just over 10 minutes to go, this is going to the wire.

Even when he does something brilliant, it's still just not happening for Damien Comer.

He brushes Brendan McCole to the floor and attempts to swing one over off his left foot. The Galway fans go wild on Hill 16, but Hawk Eye rules his attempt as wide.

Philly McMahon
Eight-time All-Ireland winner with Dublin on BBC Sport

I think Galway can be a bit more aggressive in defence, particularly inside the 45 metre line when they have all the bodies.

The fact that they have only conceded maybe one or two frees will tell you they are either not being good defending or else not getting enough hands on.

John Haughey
BBC Sport NI at Croke Park

We have 15 minutes left but these teams still can't be separated. Who wants it more?

Philly McMahon
Eight-time All-Ireland winner with Dublin on BBC Sport

That is a massive turnover. As we know Comer is such a great leader and strong physical player, and the fact that two Donegal players come in and turn that over, particularly McHugh, different physicality that he has to Comer.

A great turnover and the buzz and energy goes up another notch.

It's not Damien Comer's day so far. Galway worked the ball into him in a dangerous area, but under pressure from Brendan McCole and Ryan McHugh, he slips and coughs up possession.

There are 53 minutes on the clock and the game remains level at Croke Park.

It's level for the ninth time, as Paddy McBrearty converts from a free.

However, there is bad news for Jim McGuinness as Eoghan Ban Gallagher is forced off with a hamstring injury. Jeaic Mac Ceallbhui comes in for the corner back.

Philly McMahon
Eight-time All-Ireland winner with Dublin on BBC Sport

They just missed the opportunity.

Every time they made another pass, Donegal players are coming back and back.

They key for Galway, if they want the probability of getting a shot off, they need the ball quicker in direction of the Donegal goal.

Liam Silke puts Galway ahead after a well-worked score.

It's score after score after score. Galway respond to a Donegal point once again, with a fisted effort from Dylan McHugh.

It has been a quiet afternoon for Paddy McBrearty, but he steps up with a wonderful curled score from range.

Philly McMahon
Eight-time All-Ireland winner with Dublin on BBC Sport

Again, that's the danger of not having two or three players to back you up.

If you're one v one it just takes a little side step, and as you're defending, you are going to step off a little bit.

Donegal's lead doesn't last too long as Cillian McDade replies for Galway.

Shane O'Donnell puts Donegal back into the lead.

Philly McMahon
Eight-time All-Ireland winner with Dublin on BBC Sport

Galway are playing with fire here. Not having an extra-man, not having a sweeper because they are holding those bodies up.