Kirwan's strategy during his troubled three seasons in charge was a constant competition for places which left some players down on confidence and unsure of their place in the side. In 2014, Hickey, West, Benji Marshall and Chris Noakes were all tried in the No10 jersey.
This year West will be vying with the inexperienced Matt McGahon and Piers Francis for the first-five spot, and the expectation is for him to take control on and off the field.
"Ihaia West is the guy who has been in Super Rugby for three years," Umaga said today. "I was very impressed with him in last year's ITM Cup. The growing of Ihaia [could be seen] in that kick to win the game. Some people have had issues with Ihaia's mental temperament - being able to handle pressure situations. I just thought his game had grown in the ITM Cup.
"He is the senior 10 there so it's his job to lose at the moment... but everything's open."
Umaga, taking time out from leading his team in their pre-season training activities, was wary about promising much in his first season - another big difference to the relentlessly positive Kirwan.
West's halfback partner is likely to be Bryn Hall, who will have Billy Guyton and 19-year-old Sam Nock as his rivals for the position.
Umaga said: "I know [Hall] didn't have such a good 2015 but I have talked to him about 2014 when he was very good and how he can get back to that."
The Blues' World Cup-winning All Blacks, prop Charlie Faumuina and skipper and loose forward Jerome Kaino, have been training with the team, with Japan-based players, flanker Tanerau Latimer and utility back Male Sa'u, due to arrive in a fortnight.
Midfielder Rene Ranger, back at the Blues following his stint in France, has yet to resume contact training following neck surgery. Umaga is hopeful the 29-year-old Ranger will be available for the team's first game against the Highlanders at Eden Park on February 26.