According to TMZ Sports, former NFL cornerback Brandon Browner joined them, and all three players are set to compete when games begin April 15.
Hardy last played in 2015 for the Dallas Cowboys, registering six sacks in 12 games.
The 28-year-old was named to the Pro Bowl in 2013 when he posted 15 sacks for the Carolina Panthers, but he appeared in just one game the following year due to a domestic violence conviction.
The case against him was later dismissed, however, when the accuser did not attend the appeal hearing.
Hardy nearly signed with the Salt Lake Screaming Eagles of the Indoor Football League last week, but the team's fans voted against bringing him in.
The 33-year-old Winslow hasn't played in the NFL since appearing for the New York Jets during the 2013 season.
The former No. 6 overall pick of the Cleveland Browns made one Pro Bowl during his career, and topped 1,000 receiving yards in 2007.
According to The Spring League's official website, the league will consist of four teams, and six games will be played.
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