De Rossi is being linked with Manchester City.
Zeman said: "I don’t know why his start to the season has not been great, you could have many theories. Perhaps he was disturbed by the rumours at the start of the season, those reports that he was or wasn’t right for Roma, that Manchester City wanted him... That can influence a player.
“Personally, nobody has asked me for De Rossi. Some people say there are 10-11 clubs interested and I have a few doubts on that.”