The Tractors Boys won via goals from George Hirst, Jack Clarke (2) and Jaden Philogene.
“There were some positives out there, for sure,” said McKenna. “Some really good individual performances, players who showed the growth that they’re making in their careers really, with the level of performance they put in.
“And as a team there were some good things, especially in the first half. Put some good moves together, cut through the pitch on a few occasions and looked a goal threat. So we were good value for the lead.
“I think the second half could have been better. We got the goal fairly early in the half which probably put the threat of the game to bed and we made some mistakes, but the game was pretty comfortable and we still defended our box pretty well.
“There are some tired bodies out there who got some really good minutes in, so there were lots of good things and really nice to be through to the next round.”
On Clarke, McKenna continued: “I think it’ll be a boost for him, but I’ve got no doubt about Jack’s qualities.
“He’s showing it in training, there have been signs of that performance in training, his understanding of everything in terms of the position, how he can affect the game, the demands of our group. His understanding of that is really growing.
“I’ve said it before but you can’t underestimate the jump and the change for someone like Jack and we’ve probably got a few players in that category, who were signed late in the transfer window into a new group, have never played in the Premier League, joining a club that hasn’t been in the Premier League for 22 years.
“And trying to settle into all that change in the toughest league in the world as an attacking player is not easy.
“We know how talented he is, he’s a player we’ve signed to help us this year, which he is, and for the future as well, and I’m sure he’s going to keep improving and I think today was not a big surprise to me.
“I thought he showed some really good qualities and he was very, very difficult to handle today and his work off the ball was outstanding, which I think is a big, big jump forward from what he was doing over previous seasons as well. He’s making good progress and today’s a good little boost for him.”