Merrick will be in charge of his 200th match in the competition, and his 49th with the Phoenix, after 151 games with the Melbourne Victory, whom he took to two titles.
"It was quite amazing when I didn't think I would be a coach in the first place," he said.
Scotland-born Merrick said he initially turned down the job at Doveton in Victoria when he was approached before finally agreeing to be player-coach.
After he had coaching spells with other clubs and with the Victorian Institute of Sport, his career took him to the Victory in 2005.
The Victory's title-clinching win over Adelaide United in 2007 remains an obvious highlight.
"That is never going to happen again - winning the grand final 6-0 and one player, Archie Thompson, scoring five in front of a record 56,000 fans at Etihad Stadium," he said.
"If ever everything went right on the night, that was it for us."
After a stint as Hong Kong coach, Merrick joined the Phoenix at the beginning of last season.
"I could see tremendous potential in New Zealand as there was an opportunity to have not only Wellington behind us but the whole of New Zealand," he said.
"I also think we are everyone's second team in Australia because they want us to knock off their rivals."
