Wylie had given WaiBOP a 14th-minute lead with a quality free-kick but they trailed Hawke's Bay 2-1 at halftime after goals to captain Ross Haviland and Sean Lovemore.
Coombes said he felt his side started well but Wylie's dismissal and his side's reaction to it was key in the outcome.
"The first 25 minutes I thought we started where we left off against the Phoenix," Coombes said.
"We were rolling the ball around and we were quite confident and scored a goal.
"But that goal almost came at a bad time because I think we dropped our standards and stopped playing our game and we dug ourselves a hole."
WaiBOP United 2 (Craig Wylie 22', Chad Coombes 57') Hawke's Bay United 4 (Ross Haviland 29', Sean Lovemore 41', 72', Ryan Tinsley 75').