Delap scored from the spot to help Ipswich to a famous 2-0 win on Monday.
“It was an outstanding team performance, there were so many outstanding individual performances in there, but Liam was fantastic tonight, there’s no doubt about that,” McKenna said.
“I’ve been saying it to people around the club, he’s improving. He’s a different beast now to what he was in July and when you see that rate of improvement from a 21-year-old, showing the increased maturity that he is, the desire he’s showing to improve, that’s a really positive sign at 21. He’s done a great job tonight and all season really.”
On Delap's England chances, McKenna also said: “I don’t think he’s thinking about that.
"Liam’s a funny lad and he’s good at staying in the moment. He’s enjoying his football, he’s enjoying the group of boys he’s in the dressing room with.
“He comes into training, he wants to have fun and now he wants to get better as well and he’s trying to improve every day, and he’s trying to take on the challenge of playing in the Premier League.
“I also spoke to him today about taking on the challenge of leading the team because when you’re that number nine in the team with the dynamic of where we’ve come from, it’s a lot of responsibility from a leadership point of view.
“And he’s just enjoying the challenges. I think he’s taking each day as it comes and he’s not focusing any further than that. I think that’s exactly the right thing to do.”