The 18-year-old midfielder was tipped for a first-team role earlier in the season but an issue picked up in the summer delayed his arrival.
“It was an incredible start for Mainoo," he told BettingOdds. "Especially considering he has just come back from an injury.
"He showed confidence, willingness to receive the ball and had great positioning which at a young age is very impressive. It’s a good start, and now he needs to find consistency in his game to reach the top.
"He will have to lean on the more experienced players like Casemiro and Amrabat, both of which can really help his development.
"We can see straight away he has so much quality and he will be an incredible asset for Manchester United and Erik ten Hag, because he needs players like Mainoo who are energetic and aggressive."
And Saha reckons that a fasttrack into Gareth Southgate's senior squad may also be on the cards ahead of Euro 2024.
"If Mainoo brings consistency and keeps playing at a high level then he could definitely give Southgate something to think about."