Jose Mourinho admitted he was "a little scared" amid speculation of Nicolo Zaniolo leaving Roma, while he refuted suggestions the attacker was difficult to manage.
Zaniolo scored the winning goal as Roma ended a 14-year trophy drought, defeating Feyenoord in the inaugural Europa Conference League final in May.
But speculation persisted in the close season that the 23-year-old may depart the Eternal City, with Juventus reportedly the favourites to secure his signature.
Zaniolo dismissed the move as never likely ahead of Thursday's Europa League clash with HJK Helsinki, which Roma won 3-0 after goals from Paulo Dybala, Lorenzo Pellegrini and Andrea Belotti.
While the Italy international suggested a transfer was never on the cards, Mourinho acknowledged he was nervous he could lose one of his brightest prospects.
"The director [Tiago Pinto] never came to me to tell me: 'this possibility exists'. Never. You read so many things, especially in the summer," the Roma coach told reporters after victory over HJK.
"I knew he was an important player for us, with different qualities than the others. He's the only one with this physical potential. Yes, I was a little scared.
"He's a good guy, they told me he was a disaster as a professional. Either it was lies or he changed. I have never seen him arrive late, never had problems."
Roma sit three points behind early pacesetters Real Betis in Group C, with Ludogorets in second after defeating the Giallorossi on matchday one.