The defender was a surprise starter earlier in the season and the youth coach has noticed the change.
The young defender has had a tough start to his Magpies career since joining from Servette in 2013, with a string of injuries having hampered his game time.
He failed to impress in a loan spell with Rangers last season as well and many thought he would likely leave the club at the end of this season when his contract comes to an end.
Mbabu was surprisingly thrust into the first team against Sheffield Wednesday in September, and then featured in the Premier League against Chelsea and Manchester City, and Beardsley says they have transformed him.
"What I have noticed is a change in Kev since the start of the season," he told nufc.co.uk.
"To be fair to him he's been top class. Nobody was prouder than us when he got the chance to make his debut against Chelsea.. His emergence is great news for us."
The defender could also be featuring in the first team again this weekend when they take on Bournemouth, with right back Daryl Janmaat struggling with injury.
Given how poorly Newcastle’s first team stars have performed this season as well, there is an argument that Steve McClaren should turn to the youngsters to try and turn things around.
Indeed, youngsters such as Aleksandar Mitrovic and Ayoze Perez have been some of their better performers so far in this campaign, suggesting the manager would have no issue turning to Mbabu again if needed.