Lascelles worked with McClaren during his time at Nottingham Forest, although he admits he didn't have too much contact with the man back then.
But the 21-year-old nevertheless insists he is impressed by what he knows of his boss - especially what he achieved in terms of the way Derby County played football under him. He is perhaps ignoring those crucial last few months...
He told nufc.co.uk: "When the head coach was at Forest I was 16 and still with the youth team, so didn't have too much to do with him.
"But from what I know of him, he's great at what he does. He got Derby playing some great football in the Championship, so just imagine what he can do with these boys here.
"He wants us to be professional, show the right attitude and play in a certain way. That's worked for him over the years and, with the talent in the squad here, there's no reason why we can't do really well."
Need a little help from my friends...
McClaren's coaching credentials may all be in place but the Newcastle boss won't get far without external assistance - namely the support of his board.
For an outsider, McClaren seemed very confident indeed the Magpies would throw money at summer signings when he came in. He said this was based on a Mike Ashley interview he saw on television.
So far, the Newcastle boss has been made to look as naive as that statement initially sounded, with no new Magpies signings coming through the door as of yet.
In the coming weeks, then, the club really need to get behind their manager, or he could end up suffering the exact same fate he did at both Nottingham Forest and Derby.