"We have to back each other up and know what your mate's going to do."
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Williams was a standout for the Blues for his workrate and ability to get his offload away to West in the final minutes when everything was on the line.
"Sonny Bill is obviously still coming back from 18 months away from the game," Umaga said. "He's had a stop-start season for us. We really wanted him to play 80 minutes because of what he can bring. Every week he gets better and better. We saw a step up and I think that shows the hunger that he's got to play at the top level. He was very good for us and that's got to be pleasing for the All Blacks.
Blues skipper James Parsons was ecstatic about a performance which he said stayed true to the team's style.
It shows how dangerous they can be if they align their natural flair and running game with discipline and structure. "Blues rugby won us that game," Parsons said.
"We set a platform and then Steven and Sonny took over and then Ihaia off the bench. That's the most pleasing factor - we played our game, our style.
Umaga, asked if it was his proudest moment as Blues coach, said: "I'm always proud of these guys.
"It was another proud moment for me and the players and the club to get that result and the way they fought that hard until the end."