Kolarek had his contract selected from Triple-A Durham on Friday, Marc Topkin of the Tampa Bay Times reports.
Kolarek has been quite good for the Bulls this season with a 1.70 ERA, 0.99 WHIP and 50:10 K:BB over 42.1 innings. The 29-year-old lefty's only big-league experience came in a 12-appearance stint with the Rays last season, in which he allowed six runs across 8.1 innings.