The XFL has more than 100 players participating in combine-like drills at a Summer Showcase in Montclair, New Jersey.
Receiver Hakeem Nicks, quarterback Joe Callahan, running back Branden Oliver, receiver/running back Dexter McCluster and running back Andre Williams are among those taking part in the tryout.
The new professional league is holding showcases at various sites around the country in preparation for its relaunch in 2020.
Nicks, 31, spent seven seasons in the NFL after the Giants made him a first-round pick in 2009. His final season of game action was 2015.
Callahan, 26, has played one game, seeing action in a 2017 game with the Packers. He also has spent time with the Bucs, Eagles, Browns and Saints.