Adomah, 28, joined Villa on deadline day after three seasons at the Riverside.
The Ghana international played an influential role for Boro as they secured top-flight status.
But he opted to stay in the Championship after completing a three-year deal with relegated Aston Villa with youngster Adama Traore moving in the opposite direction.
But manager Aitor Karanka says the future will show whether he was wrong or right.
‘The future will show. If Adomah plays 200 games and gets 50 goals and Traore doesn’t play, I have made a mistake,” he said
‘I will be happy if he is successful at Villa and if Traore is successful here.
‘Traore is younger. I can bring a lot of things from him to increase his value.
‘His value is now less than last season. But with me and his team mates, he will increase his value for the club – not just for the team.’
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