"We can't be this Jekyll and Hyde team anymore," Plumtree said.
"This hot-and-cold performance won't cut it against Leinster this week. They will punish us and not let us off the hook. As good as Zebre were, they gave us some soft moments and we won't get that from Leinster.
"We will have to be better in every aspect of the game," Plumtree said, before adding with a wry smile, "Leinster won't be scared of us after this game."
The Sharks were impressive in some areas but poor in others. That is pretty much a reflection of their season and it confirms that they are a team that is some way off maturing.
And that is fair because it is 18 months since Plumtree returned to Durban from New Zealand to begin his second stint at the Sharks, and it takes longer to build a team and then to hit your straps, especially considering Plumtree started at ground zero.
A notable area where the Sharks have gone off the boil is the aerial contest. They were renowned for the accuracy of their contestable kicking and their success rate in getting the ball back, but they were nowhere with their kicking game and Plumtree agreed.
"Our kicking wasn’t good and our inability to win our contestable kicks hurt us," he said, before adding a telling comment: "Some of our backline combinations did not click...