"He's the first one to admit he's not quite ready so that was probably the biggest selection situation we had.''
Marshall will cover first-five and fullback.
"We wouldn't put him on the bench if we didn't think he could cover both roles pretty competently so we've got him there to cover that,'' Kirwan said.
Another key selection is at loosehead prop where Ofa Tu'ungafasi will make his first start for the Blues after impressing the coaching staff during the pre-season. Tony Woodcock is unavailable for the match, as is fellow All Black Keven Mealamu.
"Ofa Tu'ungafasi has had an incredible pre-season and just really deserves his spot. What you've seen from Ofa in the pre-season is heaps of energy, excitement and him throwing himself into everything,'' Kirwan said.
"I think the biggest thing for Ofa is the invisible stuff that people don't see. He's really taken control of his diet, he's lost 10 kilos, he's much more settled as a person, he's really matured and understands what he wants and that's reflected in the way he's trained. He's reaching PBs and also the way he's playing, he just needs to get out there this weekend and keep that energy up.''
Veteran Tom Donnelly will play his first game for the Blues against one of his former teams, and he is joined in the locking department by Liaki Moli who has risen to the challenge in the absence of the injured Culum Retallick.
"Liaki's had another good pre-season. He's been really fit, he got a little bit of an injury which put him out of the second game but Liaki is a player that we're expecting to play really well this season,'' Kirwan said.
Despite producing a number of fine performances at centre during the pre-season, George Moala reverts to the wing for Saturday's clash as Kirwan has gone for the experienced combination of Francis Saili and Jackson Willison in the midfield.
The Blues team to face the Highlanders at Forsyth Barr Stadium on Saturday, kick-off 7.35pm is: Charles Piutau, Frank Halai, Jackson Willison, Francis Saili, George Moala, Chris Noakes, Piri Weepu, Peter Saili, Luke Braid, Steven Luatua, Tom Donnelly, Liaki Moli, Charlie Faumuina, James Parsons, Ofa Tu'ungafasi. Reserves: Tom McCartney, Sam Prattley, Angus Ta'avao, Patrick Tuipulotu, Brendon O'Connor, Bryn Hall, Benji Marshall, Tevita Li.