Cowan has started all six games for the Blues, and, while the 33-year-old former All Black adds experience to a youthful Blues backline, Kirwan has clearly decided that more speed is needed both in getting to the breakdown and passing the ball. Gibson-Park, 23, will provide that against a Chiefs team which will be favoured to extend the Blues' losing run to seven from seven this season.
Tevita Li returns to the left wing in place of Melani Nanai, with All Blacks lock Patrick Tuipulotu named on the reserves bench.
Prop Tony Woodcock has been ruled out with concussion.
Blues team to play the Chiefs at Waikato Stadium on Saturday, kick-off 7.35pm, is: Charles Piutau, Frank Halai, Pita Ahki, George Moala, Tevita Li, Dan Bowden, Jamison Gibson-Park, Jerome Kaino (c), Brendon O'Connor, Steven Luatua, Hayden Triggs, Josh Bekhuis, Charlie Faumuina/Angus Ta'avao, Keven Mealamu, Ofa Tu'ungafasi. Reserves: James Parsons, Sam Prattley, Angus Ta'avao, Patrick Tuipulotu, Luke Braid, Jimmy Cowan, Ihaia West, Francis Saili.