The most important aspect was game time for recent signings, some of the players who have recently returned from injury, and players who have been on the fringes of the first team in recent weeks.
The Iron got off to a decent start as, in the fifth minute, Kevin van Veen picked up the ball on the left side, and played it to Horsfield, who was shrugged off the ball by two players and brought down. Adam Hammill dinked the subsequent free-kick into the area but it was cleared.
Two minutes later, Tom Pugh played the ball down the right channel, which Olufela Olomola chased down but it was cleared for a corner. The corner came in but Middlesbrough cleared and broke through one of their wingers before the ball went out for a goal-kick.
In the 12th minute, Boro got the ball in space down the left-hand side and drilled in a low cross across the face of goal. The ball was then put into the danger area by the right-winger, cutting in at the back post before being turned in from a yard out by a striker to make it 1-0.
On 14 minutes they made it two, as one of Middlesbrough’s central midfielders drove forward and played the ball through to a striker, who advanced onto it and struck the ball beyond Jon Flatt.
There was a Scunthorpe chance two minutes later, as a free-kick was swung in by Clayton Lewis. It was cleared to Harrison McGahey on the edge of the area, but he fired over the crossbar.
Soon after, United came close again. They received a free-kick on the edge of the box after Yasin El-Mhanni turned two players at once and got into space before being hacked down. Lewis took it and whipped the ball over the wall, going just wide of the near post.
Then, Horsfield played a crossfield ball to El-Mhanni but his shot with the outside of his boot was headed away. The ball came back to Hammill, but he shot over the bar.
Following a lull in play, Middlesbrough broke from defence, and played from the centre of midfield out to the left. The ball was crossed into their striker, but his effort was off target.
Scunthorpe managed to pull one back in the 40th minute, as Lewis got the ball on the halfway line and played it to Olomola on the left. He passed to El-Mhanni on the edge of the box, who dummied for Horsfield, who then drilled it into the bottom left-hand corner from 25 yards.
United had another chance just a minute later. Olomola played the ball over the top of the defence for van Veen. He cut onto his right foot but his low shot from the edge of the box was saved by the goalkeeper
The home side extended their lead in the 42nd minute. The ball was played down the left channel and the Boro winger used his exceptional pace to charge through into the box and slot into the net.
There were two Scunthorpe substitutions at the half-time break, as Tom Pugh and Trialist A were replaced by George Hornshaw and Lewis Butroid.
Early in the second period, Hornshaw played a one-two with Horsfield and then Hammill got the ball and sent in a low cross from the right, but it was cleared at the near post.
In the 51st minute, a crossfield ball from Lewis found Olomola on the right, who drove past two defenders and played in a low cross but van Veen sent the shot wide.
Not long after, the ball was played down the right by Horsfield, Olomola ran on and it was cleared for a corner. Lewis took it and the goalkeeper came to gather and dropped it, but the defender nipped in front of van Veen before he could take advantage.
On the hour mark, the hosts could have extended their advantage as the ball was crossed in from the right by the home side and took a deflection off a defender before looping towards goal, but Flatt managed to claw it away.
A minute later, one of Middlesbrough’s central midfielders received the ball from the left and shot from the edge of the box, but it went well over
On 66 minutes, Butroid won the ball back on the left and squared it to Lewis, who controlled from 25 yards and had a shot at goal. The goalkeeper spilled it at the left-hand post but retrieved the ball at the second attempt.
Five minutes later, there was more good play for the Iron as Hornshaw spread play to Horsfield, who then found El-Mhanni on the right. He whipped a low cross in, with van Veen running to the near post, but the ball just had a little bit too much pace on it.
In the 73rd minute, a left-wing free-kick from Middlesbrough was floated into the box, with a striker heading goalwards but Flatt saved at his near post.
With around 10 minutes remaining, Lewis cleared from a corner to Olomola, who held the ball up and played wide to Hammill. He then cut back to Horsfield on the edge of the box and his left-footed shot was blocked by the defender.
Adam Kelsey then received some game time, coming on for Flatt in the last ten minutes. The young goalkeeper was immediately called into action as he flew to his right to push a shot from a Boro striker wide for a corner.
From the resulting set-play, the ball went to the far post and was headed goalwards. Kelsey made a save to his left but the ball came back into play. He saved the second shot but the rebound was put in from two yards.
With five minutes to go, a left-wing cross from Butroid was touched back by van Veen to Horsfield, whose drive from 25 yards was saved by the goalkeeper.
A Middlesbrough shot was cleared off the line by McGahey on 87 minutes. A powerful shot from the right looked like it had been put in by a Boro striker but United’s defender managed to clear.
The hosts made it five right on the death, as a shot from the edge of the box from a Boro attacker hit the left-hand post and rolled across the line, hitting the right-hand post before going in.
TEAM: Flatt (Kelsey, 80), Webster, Horsfield, van Veen, Lewis, Ben El-Mhanni, Olomola, McGahey, Pugh (Hornshaw, 45), Hammill, Trialist A (Butroid, 45).