These days the game is very much something he fits in and around a busy life.
With a young family and a business to run, there are not a lot of extra hours in the day.
But the veteran hooker is lining up for his 15th season and will play his 200th senior game in Dunedin when he runs out on to the field for Green Island against Southern at Bathgate Park tomorrow.
"I'm hanging in there," he said.
"Rugby is actually the easy part. Juggling three kids and a business is the hard part. Rugby is my recovery.
"My perspective has changed. Rugby used to be 95% of my life. Now it is 5%."
Mirrielees and his wife, Julie Cheyne, own and operate a gym which is convenient, otherwise Mirrielees is not sure he would have the time to work out and stay fit.
The couple have three children - Luna-Marama (4), Enya-Mahuika (3) and Arlo-Manaaki (7 months), so life really is busy.
"If you work an eight-to-five normal job you don't have time to train, so that is how I'm able to keep playing because I can keep training."
The 35-year-old spent the majority of his career with Harbour, notching 180 games and about 150 as captain. He got his start with Dunedin in 2003 and played four games for the Sharks before transferring to the Hawks.
He also had a stint with Mid-Western Rugby Club in Whangarei in 2012 and helped the club win the senior banner.
Last year he switched allegiances to Green Island.
Mirrielees also had a long provincial career. He is adamant he made 44 appearances for Otago, although the almanac suggests he played 45 games.
His favourite Dunedin club rugby memory was helping Harbour upset Southern in the semifinal in 2011.
"They had won 18 games in a row ... but we came out and pipped them."
Mirrielees also played some rugby in Scotland and Hong Kong. He had an offer to play for Northland in 2012 but chose to come home to Dunedin to establish a business and start a family.
Green Island has a tough start to the season, drawing the defending champion first up. But Mirrielees believes Green Island could surprise a few teams this year.
The side has been training hard during the off-season.
"Everyone is lifting good tin and eating good food. I think this year will be the first year in Green Island history everybody in the pack is over 100kg.
"Now we have the strength and size, it is just about executing the game plan and playing together."