Newcastle won 3-0, thanks to second-half goals from Alexander Isak (penalty), Dan Burns and William Osula. Johnson was sent off for two yellow cards in the first-half. The result confirms Ipswich's relegation.
“We’ve come here in a really difficult situation, not just in terms of the league but in terms of availability,” McKenna said. “Getting a fit squad and team out with players in the right position has been a challenge this week.
“We knew Newcastle are in fantastic form at home with great momentum and have blown the last couple of opponents away, so we knew we had to manage the game well and try and take some of that momentum away in the early stages.
“And I thought we did a pretty good job of that and carried a little bit of a threat going the other way.
“And at 11 v 11, I think we can take pride in terms of how we’ve managed a really difficult game. With 11 v 10, the challenge was just too big, so it didn’t go our way.”
Johnson not that type of player
On Johnson’s dismissal, McKenna was frustrated with the first booking being for diving.
He continued: “I think the first yellow is the key decision, in my opinion. I think we’re really frustrated with that one because as I saw it at the time, Ben Johnson’s running through, takes a touch past the last man and is running at pretty much full pelt with the ball.
“Dan Burn sticks his leg out, his foot and his knee across Ben. Whether there’s minimum contact, little contact, no contact, I don’t know, but I think it’s natural for the forward in that situation to go over the contact. You don’t have to get smashed by the defender, it’s natural to ride the contact.
“Of course, whether it’s a foul or no foul is really, really marginal and there will be 100 slow motion replays to see what contact there was that I haven’t seen, but I don’t think there’s any need to give a yellow card. It’s not simulation, he’s not that type of player, I think he’s expecting the contact when Dan Burn sticks his leg out and he tries to get out of the way of the contact.
“If the referee doesn’t think it’s a free-kick then fair enough, but to book a full-back in that situation makes it really, really difficult."
McKenna added: “The second yellow, I think in isolation you can say a yellow can be given but when it’s a player’s first foul of the game and the first yellow is a couple of minutes earlier and was very debatable, in my opinion, I’ve said that because it happened earlier in the season.
“I think a red card in football is such a big thing that there should be room for discretion in those areas when it’s a first foul and it’s very close after a very debatable yellow card.