He joined on a free transfer from Middlesbrough last summer, and rumours suggest Bristol City are one of the clubs looking at the shotstopper.
"There are at least two or three clubs who want him but they won't release their money until they have to," said manager Dave Hodgson who has offered the 22-year-old a new contract at the Williamson Motors Stadium.
"Russell had an excellent season for us but has weaknesses as well as strengths. If necessary I will sign a replacement with his strengths."
Russell had a loan spell at Glanford Park at the beginning of the 2003-04 season, making eleven appearances.