And Hawke's Bay paid for that miss as Waitakere began to grow into the contest, Barnes missing a great chance - shooting wide from a handy position after a Bowen cut back from the byline.
But soon after Waitakere did pull deservedly level, referee Nick Waldron blowing for a penalty in the 23rd minute as Bowen's strength caused issues in a crowded penalty area - Butler tucking home from the spot.
The visitors survived a strong appeal for another penalty soon after as Bowen continued to cause the visitors issues with his strength and power.
But any Waitakere frustration was lessened at the 40-minute mark as Kohei Katsumoto presented Bowen with the chance to run straight at goal and, after initially rounding goalkeeper Josh Hill, Bowen was brought down by the retreating Hawke's Bay goalkeeper.
Waldron pointed to the spot and Barnes finished for 2-1.
After Waitakere enjoyed the better of the opening stages of the second half but just on the hour Hawke's Bay created their first chances since the early stages, Matsumoto's run into the Waitakere area seeing the fullback cut inside and shoot low which Robinson did well to turn behind for a corner.
From that set piece, Cory Chettleburgh drove the ball back to Tom Biss on the edge of the Waitakere area and the Hawke's Bay midfielder fizzed a first-time effort inches wide of the post.
As the final 25 minutes played out, the hosts seemed content to protect their lead and Hawke's Bay continued to enjoy more possession but outside of a Mason-Smith header which went narrowly wide, Brett Angell's team couldn't turn that advantage into regular scoring chances as they fell to their first defeat.