Toronto FC has declined options on goalkeeper Clint Irwin and forward Tosaint Ricketts.
Defender Jason Hernandez and forward Jordan Hamilton, meanwhile, will both be out of contract at the end of the year.
Toronto could still bring all four back as it could with Brazilian defender Auro and Argentine forward Lucas Janson, whose loan deals expire Dec. 31.
GM Tim Bezbatchenko said negotiation will continue with the players in question.
Toronto also agreed to terminate the contract of midfielder Ager Aketxe by mutual consent. The Spaniard was returned to his club in Spain after failing to make his mark.
Fourteen players remain under contract for the 2019 season: goalkeeper Alex Bono; defenders Justin Morrow, Chris Mavinga, Gregory van der Wiel, Eriq Zavaleta; midfielders Michael Bradley, Jonathan Osorio, Victor Vazquez, Marky Delgado, Liam Fraser and forwards Sebastian Giovinco, Jozy Altidore, Jon Bakero and Ayo Akinola.
Toronto FC's 2019 roster
Goalkeepers (2): Alex Bono, Caleb Patterson-Sewell
Defenders (8): Julian Dunn, Nick Hagglund, Chris Mavinga, Drew Moor, Ashtone Morgan, Justin Morrow, Gregory van der Wiel, Eriq Zavaleta
Midfielders (8): Michael Bradley, Jay Chapman, Aidan Daniels, Marky Delgado, Liam Fraser, Jonathan Osorio, Ryan Telfer, Victor Vazquez
Forwards (4): Ayo Akinola, Jozy Altidore, Jon Bakero, Sebastian Giovinco
