The former United stopper has been impressed by the January signing.
He told the Manchester Evening News: "I think we were all very impressed.
"The thing that impressed me most was that he always looks forward. He always gets the ball and his first thought is to pass forward and create chances, which maybe they [United] were missing before.
"He's brought that bit of quality and cutting edge to the final third and since he's come in their performances have been much better, from what I've seen."
Cathcart believes Ole Gunnar Solskjaer is getting his strategy right by filling the United squad with a blend of homegrown youngsters and marquee signings like Fernandes.
He added: "Obviously since Sir Alex left, it's been difficult for United, so I think this is a new way of looking at things. I can see this now being good for them, you can see young players now coming into the team and doing really well, so there's no reason why they can't progress and improve.
"They've obviously signed a few players as well, they've signed Fernandes who everyone's raving about. He looks a quality player and that's the mix you need, a good mix of experienced players and youth as well. I think things are looking up."
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