The pair, who worked together for several years at Brentford, faced-off on Wednesday night as Spurs won the preseason tie 1-0 in Hong Kong.
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Frank later said of his former Brentford captain: "It was a little emotional. I've known him since he was 15. He's 31 now and I've been training him for 12 years so I can say that I've known him for a pretty long time.
"This is the first time I've played against him. He played for me more than 300 games and it was a bit strange to see him on the other team.
"He's a top player and I can understand why Arsenal went for him. I'm so happy that he got this great opportunity late in his career."