The 24-year-old midfielder, son of former Aston Villa and Wolves star Gordon, has been filling in at right-wing-back for the Bucks in the absence of Brendon Daniels, with Lee Vaughan switching to the left.
Cowans only made two league starts last season because of injuries but signed a new one-year deal at the start of this month after proving his fitness and commitment to the cause.
And Cowan, whose side host Gateshead today in National League North, has been impressed by his displays at right-wing-back as he said: “It’s another reason why we decided to bring him back into the camp.
“After the season he had last year, I think we’d probably have been forgiven for shaking hands with him and moving on.
“But I have a lot of belief in Henry as a person, in his ability and his versatility.
“We spoke a lot about him coming out in himself. He’s been his own worst critic and that’s the only thing that’s detrimental to him.
“His belief has gone through the roof which comes with playing games and having a manager that wants to believe in you.”
As the Bucks look to bounce back from their FA Cup exit at Leiston, Cowan added: “The phrase I keep using with him is consistent excellence.
“Henry needs to have that consistency, he can’t drop below a seven-and-a-half, with this group and the position he wants to play, he needs to be performing to that as a minimum.
“He’s aware of that and has to do it and has to maintain professionalism and level of performance if you are playing York City or Leiston. Henry is a very good individual example of what we want collectively.”