The injuries to midfielder George Moala (elbow) and Charlie Faumuina (knee) are blows. The two All Blacks are key members of the Blues and the absence of the hard-hitting Moala will rob them of a threat around the fringes and could allow the red-hot Beauden Barrett more freedom with the ball. As Wales found over the past three weeks, that generally ends badly for opposition teams.
Umaga will also want to see his team continue with the structure they've mostly stuck to this year. After the at-times chaotic performances from the Blues last season, when they won only three matches - and none on the road - under former coach John Kirwan, Umaga's message is clearly getting through.
They already have six wins this year, and, while tonight's Cake Tin game against a team in the running for a playoffs spot will be difficult, he has them heading the right way.
Also looking for improvements is Sanzaar chief executive Andy Marinos, who was in Auckland this week gauging feedback and ideas for a better Super Rugby competition.
Umaga said one change could be made to the June test window, and he wondered if it would be better to continue despite the absence of international players.
"That break in the middle of the season is tough ... possibly [we could keep] playing through," he said. "That could be a way of testing your depth and possibly giving guys game time who don't get a lot of [it]."