Here's your list of minor league free agents, who are eligible.
Jose Appleton
Juan Centeno
Cale Coshow
Isrreal De La Cruz
Yariel Gonzalez
Carlos Guzman
Wilkel Hernandez
Xavier Javier
A.J. Ladwig
Mark Leiter Jr.
Josh Lester
Henry Martinez
Gerson Moreno
Pedro Payano
Franklin Perez
Ricardo Pinto
Wladimir Pinto
Aderlin Rodriguez
Elvin Rodriguez
Jesus Rodriguez
Zac Shepherd
Gresuan Silverio
Locke St. John
Christin Stewart
Christhian Tortosa
Drew Ward
It is possible that the Tigers have worked out non-public extensions with some of these guys. For anybody you want to keep that you don't have signed to a minor league extension, you can add the 40 man roster before they declare free agency five days after the World Series ends. Many players on the 40-man roster currently would also be free agents if they are outrighted. This is an exclusive list, not to say that all these guys are candidates, but it is difficult to draw the line.
Tyler Alexander
Matthew Boyd
Daz Cameron
Jeimer Candelario
Harold Castro
Willi Castro
Jose Cisnero
Miguel Del Pozo
Michael Fulmer
Rony Garcia
Dustin Garneau
Niko Goodrum
Grayson Greiner
Eric Haase
Derek Hill
Drew Hutchison
Joe Jimenez
Ian Krol
Isaac Paredes
Victor Reyes
Gregory Soto
Spencer Turnbull