Tom Pugh was on target but the Iron's Under-23s were defeated 2-1 at Grimsby Town on Tuesday afternoon.
With three minutes gone, Lewis Butroid tried to meet Pugh with a delivery into the box from the left but the hosts managed to get it clear.
The hosts then attacked down the right and got a cross in as Sisay looked for Starbuck, but United managed to get the danger clear.
With six minutes on the clock, Kenan Dünnwald-Turan looked to latch onto a ball forward but the home goalkeeper got to it in the nick of time.
After 11 minutes, George Hornshaw sent an inviting cross in from the right which Butroid met but it was turned away for a corner. Andy Dales took the subsequent set-play which was cleared as far as the left, with a ball sent in for Jai Rowe who headed over.
A minute later, pressure from Butroid down the left forced a corner. Dales took short with the ball eventually played to Raynner Silva, but Grimsby cleared.
The hosts looked to get a cross in from the right in the 17th minute but it was blocked away for a corner. It was played into the box by Spokes but the shot by Jackson Jr was blocked away for a further corner by Hornshaw, from which they then fouled in the Iron's area.
They continued the pressure as Sam Habergham got up well at the far post from a cross and sent a header wide of the far post.
Adam Kelsey then claimed well as a further cross came in from the left.
After, Habergham delivered a great ball into the box towards Sisay, who sent a header over the crossbar.
With 27 minutes played, Spokes drilled a free-kick which was deflected wide for a corner.
The home side then broke, with Hornshaw down, as Kelsey got down well to save a low drive from the edge of the area by Sisay. Following that, skipper Hornshaw received some treatment but was fit to carry on.
Soon after there was a great save by Kelsey, who got down to his right to keep out a low drive sent in from just inside the area. United then got it clear.
With 33 minutes gone, Tom Pugh looked to send Harry Jessop away with a throughball but the Mariners managed to stop it before United won it back and the referee blowed for a foul.
With 35 minutes on the clock, the Iron won a corner on the left, which Dales sent in. Charlie Barks looked to connect with a glancing header but it drifted wide of goal before Dünnwald-Turan couldn't get on the end of it.
Three minutes later, Barks looked to connect with a free-kick taken from the left, midway through the Grimsby half, but couldn't get to it and the ball drifted out for a goal kick.
With 41 minutes gone, Dales burst away through the centre but was tackled and the ball went out for a corner, which he took but was then cleared.
Two minutes later, Grimsby went ahead as a low shot by Ira Jackson was powered low and across goal from the edge of the area, beyond the dive of Kelsey to his left.
There was a triple Scunthorpe change at the break as Kelsey, Dünnwald-Turan and Brown were replaced by Tom Collins, Dan Gallimore and Joey Dawson.
The middle of those substitutes was straight into the thick of the action as Dawson headed over the crossbar from Butroid’s free-kick delivery on the left.
With 52 minutes played, Jai Rowe sent a free-kick in from the halfway line and looked for Dales but the hosts managed to get it clear.
Then, Hornshaw sent the ball forward from the right looking for Dawson but he couldn't get on the end of it.
After 57 minutes, Grimsby won a penalty on the left side of the Iron area, but they couldn't convert it, as Collins dived down low to his right to save Spokes's shot and got a hand to it, with the ball cannoning off the post. United then managed to block the rebound and clear.
There was then a delay in play as Dales took a knock which forced him to be replaced by Oliver Lobley soon after.
On 64 minutes, Jessop chased down a loose ball and Grimsby managed to get it clear as a defender and goalkeeper nearly collided.
Grimsby then threatened down the right and sent a low cross in, with Collins saving the resultant close range shot. The rebound was then blocked away as United got it clear.
The hosts continued to press, with a free-kick sent in from the left but nobody able to meet it and it eventually drifting out for a goal kick.
With 84 minutes gone, there was great work from Dawson on the left to play in Raynner Silva, who then sent the ball to Hornshaw, His dangerous cross looking for Dawson was deflected over for a corner.
The corner was sent in from the left by Butroid and it reached Pugh, who turned the ball home from close range for the Iron's leveller.
Soon after, Butroid won another corner on the left, which was taken by the same player. The Mariners got it clear though, as Jessop looked to turn and shoot.
As the fourth official indicated three minutes of added time, Barks turned a cross from the right by the home team over the crossbar.
From the corner, the Mariners managed to score the winner as the ball from Starbuck drifted past a sea of bodies and into the net.
IRON: Kelsey (Collins, 45), Hornshaw, Brown (Gallimore, 45), Silva, Barks, Rowe, Dales, Pugh, Jessop, Dünnwald-Turan (Dawson, 45), Butroid.