Macilai was one of the new signings for the BNZ Crusaders in 2015, but a broken arm in a pre-season game meant his debut came later than expected.
Macilai learned his trade playing sevens rugby in Fiji. It was while playing for the Red Rocks Rugby Club in the Coral Coast Sevens competition in 2012 that he was spotted by Northland scouts and moved to New Zealand to play for the Awanui Rugby Club, helping them to win that year's club title.
He made his ITM Cup debut for Northland in 2013, although a dislocated elbow stymied that season. He spent some time training with the Blues wider training group in 2014 and his form in that year's ITM Cup was impressive enough to grab Crusaders selectors' attention, and saw him gain the third highest number of clean breaks and metres gained of any player in the competition.