While the defender had some of the toughest tests the division provides in recent weeks, McKenna believes in him.
The 24-year-old is being seen by some as a possible England left back in the future.
“I think Leif is adjusting well, as he has done across the last couple of years,” McKenna said.
“When he first arrived with us, he was a highly talented player but had played very few first-team games.
“He had been on loan at Bournemouth, but had to adjust to playing regularly week in and week out.
“In the last year, he had to adjust to playing in the Championship week in and week out and showed his qualities and had to be very robust and resilient as well, in terms of the minutes he played.
“And now he has taken a very big step up and was certainly very much in at the deep end, first week facing (Liverpool’s) Mo Salah, second week Savinho at (Manchester) City, third week Adama Traore (with Fulham), fourth week (Brighton’s Yankuba) Minteh, fifth week (Tyler) Dibling at Southampton – it’s a position a lot of the Premier League teams are really strong at.
“For him and his defensive game, it’s been a really big challenge but I think he has risen to that challenge well. Like all our players, and all our defenders, there are mistakes and things to learn there, but those things are good feedback.
“The important thing is that he is showing that he is learning those aspects week-by-week. And I think last week was maybe his most impactful game going forward. That is one of his biggest strengths, his physicality in terms of getting forward and the quality of his left foot.
“As the team continues to develop and improve and impose themselves in games, I think that will give Leif more chance to show his attributes and also as he continues to improve and adjust to the level, and it will individually bring out his best attributes even more.
“I think he is in a good direction and we are happy with his progress. But again, similar to what we said about Liam, it is early in the season, it’s early steps and I know he is really determined to have a strong season.”