"It's really about workloads and horses for courses," Boyd said of the switch.
Boyd said Rey Lee-Lo, who started at second-five for the Hurricanes against the Lions, took a knock to his hip in last week's game, which meant he was unable to take a spot on the bench on Saturday.
Nonu missed the game against the Lions as he awaited the birth of his third child but he said he was ready for his 145th Super Rugby outing on Saturday.
"I've found my return to Hurricanes [has been] pretty good," Nonu said. "I loved the pre-season and [I'm] pretty much looking forward to wearing the jersey and playing with my brothers.
"I feel pretty good physically. I've had a long break. I had a good pre-season and had a good January. So I've got a lot to play for, especially my family, being a father to another son."
Meeting the Bulls at Loftus is an intimidating place to play at the best of times and Nonu hasn't had the luxury of a pre-season hit-out to work off the ring rust.
"I've just got to back myself, really," he said. "I've played for a long time and believe I can get the job done. I'm just raring to go."
Nonu will pair with his long-time midfield mate Conrad Smith as part of a dangerous Hurricanes backline that is laced with All Blacks, including Beauden Barrett, Julian Savea and Cory Jane.
Having the likes of forwards Ardie Savea and Victor Vito on the bench should allow them to finish with a flourish too.