However, The News understands Shrewsbury are trying to scupper the deal and land the outgoing Pompey defender for themselves.
Whatmough's heading for the Fratton Park exit door despite being offered a new contract.
The fresh agreement would be on reduced terms, however.
Whatmough's attracted plenty of interest as a free agent and many had expected him to move to the Championship.
The BBC previously reported the Latics tabled Whatmough a ‘far mor favourable’ contract.
Shrewsbury have offered the 24-year-old a contract, though, as Steve Cotterill looks to piece together a squad capable of challenging for the play-offs.
The Shrews have already signed Luke Leahy and Matthew Pennington from Bristol Rovers and Everton respectively this summer.