Kolarek was optioned to Triple-A Durham on Friday, Marc Topkin of the Tampa Bay Times reports.
The Rays acquired Steve Cishek in a trade with the Mariners on Friday, and Kolarek appears to be the bullpen casualty as a result of the acquisition. The lefty reliever hasn't seen too much action as part of the Tampa Bay relief corps this year and hasn't exactly impressed in his limited opportunities, racking up a 5.87 ERA in 11 appearances. He'll head back to Triple-A for now, where he owns a 1.36 ERA over 33 innings.