Talismanic hooker Keven Mealamu has been named to make his first start of the Super Rugby season this weekend when the Blues host the Stormers at North Harbour Stadium on Friday.
The 102-Test veteran has come off the bench in the last three weeks following an extended break but will get his first opportunity to pull on the number two jersey in place of the injured James Parsons.
26-year-old Parsons took a blow to the neck last week against the Reds but his injury is not as serious as first thought and he is expected to be out for just two weeks.
"It was all part of the plan. Kevvie's had his long break and we've brought him back into it," Kirwan said.
"JP has done everything we've asked of him and he's been playing exceptionally well. Having his small injury means Kevvie's going to step up, he probably would have stepped up anyway and we're looking for him to get back to the great form and the great player that he is."
In the only other change to the starting XV, Francis Saili is elevated from the bench to slot in at centre as Rene Ranger shifts out to the wing.
"I think this is the best side to play the Stormers," Kirwan said.
"I spoke to Rene this morning and bringing Ces (Francis) on at centre is our best attacking side for this game and that's our motivation. There's some good firepower out wide."
Scans on Anthony Boric's neck yesterday came back clear so he returns to the bench, while Lolagi Visinia, who was named in the New Zealand Under 20 squad last week, is poised to earn his first Super Rugby cap as outside back cover.
"He's one of the young crew," Kirwan said of 20-year-old Visinia.
"We thought Albert (Nikoro) did great last week and hasn't done anything wrong, we're just picking a side this week we think will be good for the Stormers and we need to start giving these young guys some game time."
At the halfway stage of the competition, Friday night's game shapes as a season-defining one for the Blues.
Trailing the Chiefs by three points and just two points ahead of the Crusaders in the New Zealand Conference, the Blues desperately need to nail this home game to maintain their position in the top six.
But Kirwan knows it won't come easy against a physical Stormers outfit renowned for their rolling maul.
"Their strengths are they're very physical, great at mauling the ball and strangling you with a good kicking game and good pressure so we're expecting them to bring that," he said.
15. Charles Piutau,14. Frank Halai,13. Francis Saili,12. Jackson Willison,11. Rene Ranger,10. Chris Noakes,9. Piri Weepu,8. Peter Saili,7. Luke Braid,6. Steven Luatua,5. Ali Williams (C),4. Culum Retallick,3. Angus Ta'avao,2. Keven Mealamu,1. Tom McCartney
Replacements : 16. Quentin MacDonald,17. Ofa Tu'ungafasi,18. Anthony Boric,19. Brendon O'Connor,20. Jamison Gibson-Park,21. Baden Kerr,22. Lolagi Visinia