Hall was the big mover last year, capitalising on Weepu's poor form and then stroke scare with his quick running game, but Cowan has quickly put the pressure on.
"I just spoke to [the halfbacks]," Kirwan said after training yesterday. "They've all played really well in pre-season ... I'm going to play them evenly this week, starting with Jimmy, and the best guy who does his core roles well and runs the football team will get the nod for the following week, so there's good pressure on."
Kirwan made a joke about Cowan being offered a flat white coffee at Blues HQ in order to feel like he was truly in Auckland, but the coach knows the competitiveness the 51-test All Black brings is no laughing matter.
"We're enjoying what he's bringing which is leadership and voice and he's bringing a hard edge, which is what we need."
Kirwan will have all of his All Blacks - Kaino, Piutau, James Parsons, Woodcock, Charlie Faumuina and Steven Luatua - available for the Chiefs match a week on Saturday.
However, one player missing will be Dan Bowden, the former Highlander and Crusaders inside back signed by the Blues after four years overseas. Bowden "popped" a ligament in his right foot during last week's pre-season loss to the Chiefs in Whangarei and could be in doubt for the Blues' trip to South Africa for rounds two and three.
It appears Ihaia West has the inside running at No10, a problem position last season, over Simon Hickey.
Kirwan said Woodcock, who didn't play for the All Blacks last year because of shoulder problems, had enjoyed a full pre-season and would play in the final warm-up match tomorrow.