"There's a lot of work to do, there's a lot of recruiting, a lot of retention work and a lot of work on your development. So it can take time."
The 3-0 Hurricanes will host the Blues in Palmerston North on Friday when they put their unbeaten record on the line, while the Blues would give anything to snap out of their funk.
"He's got a good squad. He knows that he will work it all out," Plumtree said of Kirwan.
"He's got some good assistant coaches there and they'll be looking to get their stuff together for this week against us."
Despite their contrasting results, Plumtree insisted the Blues would be a test for his side.
"Teams have this. There's not too many experienced coaches out there that don't go through these patches. Teams go through these patches," Plumtree said.
"It's the start of the season for them, they haven't done that well but they'll know it just takes that one win to kick their confidence in to gear and get on with that."
Plumtree said returning from their tour of South Africa and Australia - where they beat the Lions, Bulls and Force - and walking in to a bye was a blessing for them.
"We feel lucky that we had that week off because of the fact we came off the travel."
There are no injury concerns in the Hurricanes camp and lock Jeremy Thrush, who has been laboured with a calf problem, could make his first appearance of the season against the Blues.
The Hurricanes also have to juggle giving their All Blacks a rest and head coach Chris Boyd recently hinted that they may rotate more players out for this week's game.
"This is a big conversation for us every week as coaches," Plumtree said.