Frank worked with Mbeumo for six years at Brentford and admitted he remains a huge admirer of the 26-year-old, who joined Manchester United from Brentford in a 71 million pound deal during the summer.
Tottenham were among the clubs interested before Mbeumo opted for Old Trafford.
"He is a very good player," Frank said when asked if he had wanted to bring Mbeumo to Spurs. "He's playing for Manchester United now, and I'm very happy for him. Looking from the outside, maybe I'm a bit biased, but I think he's been their best offensive player."
Frank went on to highlight the Frenchman's all-round qualities. "He can create, he can score, he works hard, and he's a team player. He's confident but humble, a top player. He's got pace, he can dribble, he can cross, he can finish, and he always helps defensively. He's close to being the complete winger."
Mbeumo has been in exceptional form under United boss Ruben Amorim, earning the Premier League Player of the Month award for October after a series of standout performances. With four goals and one assist in ten league appearances this season, he has become the focal point of United's attack.
Tottenham, who are looking to end United's four-match unbeaten run of three wins and a draw, will need to contain Mbeumo's threat if they are to secure a result. Frank acknowledged as much, admitting his side must stay disciplined.
"Stop Mbeumo, and we have a chance," the Dane said. "If he gets space, he can punish any team."
Bryan Mbeumo could soon face one of the biggest decisions of his career, whether to represent Cameroon at the 2025 Africa Cup of Nations in December or stay with Manchester United during a defining period of their Premier League campaign.
Pep Guardiola has said he "misses" his long-time rival Jurgen Klopp as the Manchester City manager prepares to mark his 1,000th game in charge this Sunday.
David Moyes has voiced his frustration over Thierno Barry's growing pains at Everton, criticising the striker's rash tackling and lack of discipline that have already cost him valuable minutes on the pitch.
Mikel Arteta has described Granit Xhaka as "one of the signings of the season" ahead of Arsenal's reunion with their former midfielder when they face Sunderland at the Stadium of Light on Saturday.
