The theory was those players would be the first port of call for franchises who needed to bolster their squad numbers if injuries struck or players needed time off.
By his own admission, Mitchell didn't arrive in Wellington in playing shape but that changed quickly.
"I thought that was me for the year, to do all the pre-season training that everyone hates and be back home on the farm or something," Mitchell said.
But as the pre-season came to a close, second-string hooker Motu Matu'u suffered a calf problem.
And when wider training group hooker Leni Apisai wasn't deemed up to the task, Mitchell went to South Africa with the Hurricanes. The 26-year-old, who is still working towards becoming a qualified plumber, was sent home to the farm in Gore for a week in March but, when Coles suffered an elbow injury against the Blues in round five, Mitchell was called back.
He has been in Wellington since and, following recent news that Matu'u (knee) and Apisai (concussion) would be out for the rest of the season, Mitchell has made the best of it for someone not wanted by anybody eight months ago.
"It's been a bit of an up-and-down ride, to be honest," he said of the season.
"I'm very grateful for the opportunity that I've had with these guys, so, hopefully, I push for a spot next year."
Mitchell has logged eight appearances off the bench this season - he made 12 for the Highlanders in four years - and will start there again when the Hurricanes meet the Highlanders in a top-of-the-table clash in Napier tonight.
He has re-signed with Southland for this year's ITM Cup so he can play alongside his brother, prop Morgan.
"I thought it'd be quite cool to play with him and then Mum doesn't have to watch us play against each other," he said.
