Drums beating for Tana at Blues
Umaga took over in 2015 but has failed to improve the Blues, who won the last of their three titles in 2003 and have not made the playoffs since 2011.
New Zealand Herald columnist Chris Rattue led the charge against Umaga in the wake of a 19-21 loss to the Chiefs over the weekend.
"The Blues are a shambles and Umaga doesn't have the goods as a Super Rugby coach.
"This is so obvious that it doesn't even count as an opinion. It just is," he wrote.
Umaga's status as an All Black legend should keep his critics at bay for now, but his predecessor John Kirwan found that national glory won't save underperforming coaches.
The Blues' only victory of the season was a 38-35 win over the Lions in Johannesburg in Round Four.
Defeat to the Sunwolves in Tokyo next weekend – a fixture the Blues lost last year – could seal his fate.