"We didn't know our way around too much to take him to [private] doctors so we decided to take him to hospital where they were going to be more thorough," he said, adding it was more a case of "being cautious" than anything else.
At the hospital routine checks were conducted, including blood tests, before he was discharged.
Evans said the team wanted to ensure Hager wasn't carrying any sort of virus that was likely to affect the players.
"There was concern Mark might have had a little flu and that would have posed a storm of issues ... "
Evans said Hager, in the mould of coaches in every other code, had not slept too well on Friday night, got up at 4am to do work pertaining to his semifinal plans and also had skipped breakfast.
Hager and Hockeyroos counterpart Adam Commens especially appeared to be highly strung throughout the week-long tourney which was part of the third annual Hawke's Bay Festival of Hockey.
Evans said the New Zealand coach had followed the advice of the doctors and felt fine the next day.
Hager was at the warm-up routine with his players for the 5.15pm final on Sunday and then appeared again for the ritualistic after-match pep talk as well as the speech and medal ceremony.
His presence at the dugout during the game was minimal as his support staff conducted matters.
He had had a couple of beers with the players after the victory on Sunday night and was feeling much better, he said.
Coaches, especially the Rio Olympic-bound ones from New Zealand, Australia, China, Japan, South Korea and India, were using the Bay tourney as a stepping stone to the big Brazilian stage in August.
The Black Sticks are expected to play in an Aussie series, involving India and Japan, in Darwin from May 30 to June 5 before the Champions Trophy in London from June 18-26.
Maryborough-born Hager is a former field hockey player from Australia who competed in two summer Olympics for his country and won bronze with the Kookaburras at the 1996 Atlanta Games.
He has been coaching the Kiwi women since 2008.
Hager's profile:
Some highlights of Mark Hager's coaching career that included numerous Olympics:
* 2008 Beijing Olympics: Ast coach Australian men (bronze).
* 2009 8 Nations: Coach Australian U21 men (gold).
* 2007 Youth Olympics: Coach Australia (gold).
* 2004 Athens Olympics: Ast coach Australian women (5th).
* 2003 Champions Trophy: Ast coach Australian women (gold).
* 2001 Champions Trophy: Ast coach Australian women (bronze).
* December 2008: Appointed New Zealand women's coach.