The 24-year-old will be a free agent next month and is expected to move on following the Canaries' relegation to League One.
But Championship rivals Derby are among a number of clubs thought to be interested in Croft and Warnock expects the Rams to win the chase for his signature.
However, Warnock still wants to speak with Norwich boss Bryan Gunn and is now being linked with another Canaries midfielder, Wes Hoolahan.
"Croft is one we are interested in, but it looks like he is going to Derby," Warnock told the Croydon Advertiser. "I still need to speak to Bryan about other matters."
Warnock could use striker Alan Lee, who spent the end of the season on loan at Carrow Road, as part of any swap deal.