Kolarek agreed to a minor-league deal with Tampa Bay on Wednesday, Marc Topkin of the Tampa Bay Times reports.
Kolarek appeared in 12 big-league games for the Rays this past season, allowing six earned runs off nine hits and four walks while striking out four in 8.1 innings of relief work. The 28-year-old spent most of the season in Triple-A Durham, where he posted a 1.65 ERA and 46:16 K:BB in 41 games, and will likely begin the 2018 season back with the Bulls.