The striker, brought in on an initial loan until Christmas from Solihull Moors, made a big impression on his new supporters with a bustling debut against leaders York.
Cowan revealed his summer target has raised the standards in his squad and it is now up to Stenson’s new team-mates to rise to his level.
“It was nothing I did not expect,” said Cowan of his new striker’s impressive display.
“He was my main target in the summer and we weren’t able to get him over the line, it’s been a little later than we hoped.
“He did very well and we expect him to do so. Everybody has started to wake up and realise it’s not going to be easy here and you have to work extremely hard.
“He’s just laid down the gauntlet to the rest of the players by saying ‘I’m here now and you have to come along with me because I’m going to be successful’.”
The Bucks chief praised the ‘old-school’ character of former Barwell and Leamington man Stenson, whose rise through the divisions has been rapid.
“He’s not only a good player, he’s a brilliant old-school type of character,” added Cowan.
“He is very demanding of the players around him, he has that element of belief-slash-arrogance and can win matches himself. That effort (that hit the bar) was completely outlandish and if it was in the Premier League it would be spoken about constantly.”