The Counties Manukau man recorded a 40m sprint time of 4.78 seconds in team testing, faster than any other member of the squad and, according to Rennie, faster than anyone in the Kiwi conference.
"He's the quickest man in New Zealand rugby," Rennie said. "Anything under 5 [seconds] is quick and there would be no one quicker than [Pulu] in the country."
Pulu's time tracks well with some historical data unearthed. Springboks wing Bryan Habana, for example, owns the Stormers' record with a run of 4.77s and, while the time of a fellow flyer like Waisake Naholo is unavailable for public consumption, only some all-time speedsters hold a significant edge.
Former Chiefs outside back Sosene Anesi reportedly posted the fastest 40m time ever recorded in New Zealand rugby, clocking a blistering 4.53s, and All Black great Joe Rokocoko once managed 4.66s.
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At whichever point Pulu stops the clock, he will certainly provide a difficult task for any defender to cover, although the 27-year-old was more bashful than boastful when asked about his coach's claims.
"You don't want to go out there and say you're the fastest and then have someone burn you on the outside," Pulu laughed. "You don't want to brag about it or anything but I'm quite quick. I don't know if I'm the fastest man in New Zealand rugby but I am quick."
Pulu's first run with the Chiefs was anything but quick in arriving. After fitness last season limited his opportunities as part of the Chiefs' wider-training squad, Pulu's ankle injury on the first day of pre-season saw him suffer a succession of ailments and leave the wing facing a battle both physical and mental.
"It's been 18 months to get to this day," he said. "It does tend to get on top of your mind but I have good boys around me and great family members who keep me going. And just the dream of pulling on a Super Rugby jersey was at the top of my head and keeping me going."
The dream was complete in Hamilton on Saturday, with Rennie as happy as anyone to see the speedster unleashed.
"We've got a lot of time for Toni," he said. "He's had an unbelievable attitude, incredibly positive for a guy who could have just about thrown it in with the string of injuries he's had."
Pulu will be near the top of the queue to take the No14 jersey against the Brumbies on Saturday night and, if he does earn his maiden start, Rennie will be only one observer keen to watch the fastest man in New Zealand rugby fly.
Some of sports' fastest 40m times
• Hector Bellerin (football, Arsenal) - 4.41 seconds
• Sosene Anesi (rugby, Chiefs) - 4.53s
• Usain Bolt (athletics) - 4.64s*
• Joe Rokocoko (rugby, All Blacks) - 4.66s
• Bryan Habana (rugby, South Africa) - 4.77s
• Toni Pulu (rugby, Chiefs) 4.78s
*Split time in 100m world record
