The right-hander made only two appearances in the Frontier League with the Washington Wild Things before agreeing to terms with the Cubs.
With Washington, Rivera posted a 3.00 ERA in only two appearances. This past spring at Virginia Wesleyan, he fanned 64 and walked only 18.
Rivera becomes the second VWC player to sign with the Cubs this summer. Recently, the Cubs added catcher Matt Hudgins as a non-drafted free agent.
Both players were signed by Cubs area scout Billy Swoope.
Rivera, listed as 6-foot, 205 pounds, and Hudgins were named the 2007 Old Dominion Athletic Conference Pitcher and Player of the Year, respectively.