Johnson was Spurs’ leading scorer in 2024-25, with his 18 goals including the winner as the London club beat Manchester United in the Europa League final.
But he has found himself struggling for game-time under Frank, who took over from the sacked Ange Postecoglou in June.
Johnson makes a fifth Premier League start of the season as Spurs host Manchester United on Saturday having pressed his case with a goal in Tuesday’s 4-0 Champions League win over Copenhagen.
But Johnson then made himself a potential quiz question subject by being sent off, as he became the first British player to score and see red in Europe’s top club tournament.
“It’s been a change for him with a new manager coming in,” said Bellamy, who is preparing for November World Cup qualifiers against Liechtenstein and North Macedonia.
“Last season wasn’t a great season for Spurs, but he excelled in certain parts and his numbers and goals were exceptional.
“I’ve been there myself and it’s difficult when someone new comes in and you see one or two other players come in. So I feel he’s adjusting to that and the new manager is adjusting to him as well.
“I always believe quality will shine through and for Brennan I’m sure that will be the case.”
Wales go to Liechtenstein on 15 November and host North Macedonia three days later.
Wales are three points behind North Macedonia, who lie second in Group J, though Bellamy’s side have a game in hand.
Having earned a World Cup qualifying spot in the Nations League in March, Wales would be have a home play-off semi-final if they can secure second in the group.