The Millers breezed into the knockout stages of the competition as Tuesday night's victory saw Paul Warne's men finish the group stages with three wins from three.
It was not until the 51st minute that the first goal arrived as Will Grigg found the back of the net before Kieran Sadlier claimed a hat-trick, with youngster Jake Hull also scoring.
Rotherham opted to field a mix of youth and experience, with Hamshaw feeling there is plenty of healthy competition for places within the Rotherham squad.
“It was a really good win in the end. To be honest, it was a really difficult game in the first half, they moved the ball really well, which we told the players they would do," reflected Hamshaw.
“You can see how technically good they are, so it was a tough test. Once we got in at half time, we tweaked a few things tactically and came out strong in the second half.
“We had a number of young players testing themselves against talented academy lads, the game ticked a lot of boxes.
“You want competition for places, but they are fully aware that the lads in the team at the minute are playing really well.
“That is what we want. We want headaches and we know what the squad are capable of. No matter who we play, we’ve got a really competitive squad here.”