Thorson signed with the Giants' practice squad Tuesday, Dan Salomone of the Giants' official site reports.
Thorson will provide some emergency depth at quarterback, as Daniel Jones (neck) is considered doubtful and Mike Glennon (concussion) is questionable for Sunday against the Chargers. With Jake Fromm on the 53-man roster and Brian Lewerke also on the practice squad, it's unlikely Thorson would be active Sunday if Jones and Glennon were to miss.