Players were heading back to halfway for the restart when Mataira collapsed and the Maddison Trophy fourth-round match was called-off with Tech leading 33-10 midway through the second half.
Whyte said club members and brothers Tane and Tama Cooper, a Hastings fireman, worked on CPR to revive the player.
"It was pretty emotional, I understand he stopped breathing, and Tane and Tama worked on him, and a doctor tied up with Tech came in to help," he said.
"They were working on him right up to the time the ambulance arrived, it was touch-and- go, and it was a relief when the feedback from the ambulance officers was that he had been able to say his name when he was in the ambulance."
Among those on the field was former All Black Zac Guildford - back with original club Tech and having played against Mataira several times over the years - who described it as "pretty sobering" to see "Big C" go down.
Players gathered around to help save their teammate, with two in particular working on Mataira for at least 10 minutes before an ambulance arrived.
"They [the players] did a miraculous job to bring him around," said Guildford, adding it brought back memories.
A teenaged Guilford was about to celebrate his New Zealand team's win in the 2008 Junior Rugby World Cup in Japan when his father Rob, a Tech stalwart, died in the grandstand.
Dan Somerville was at the game and, while not close enough to see the response at close-quarters, said: "Teammates and medical staff did an amazing job to keep him alive, he was revived at the scene."
Mataira has been regarded as one of the ultimate club stalwarts, and, while continuing to play mainly in lower senior grades, also put his boots on to play - again as a substitute - when Tamatea, having finished at the bottom of the Premier competition ladder in 2018, successfully defended its status with a promotion-relegation win over Otane.