Which is where Kerr-Barlow could prove his worth. The 23-year-old enjoyed his first action of the season against the Highlanders, having a busy night on both sides of the ball and probably shading the clash of All Black halfbacks.
While he ran the ball well down the short side, carrying 17 times for 56 metres, Kerr-Barlow's value on defence was illustrated in the Chiefs' haste for him to return to duty for the final five minutes after his head knock.
"When you're leading by a couple of points you're pretty keen to have him on the field," Rennie said. "He's probably the best defensive 9 in the competition."
It is an area of his game in which Kerr-Barlow prides himself, though that is more about a desire to inject himself in among the action, rather than any predilection for defence.
"I just like to be involved in the game in any way I can," he said. "Obviously, I love running with the ball, it's probably my favourite thing to do, but if I can, I like to be involved in the game just defensively.
"I like being really physical, so it's just another avenue where I can be involved."
His involvement on defence will again be important against the Stormers but, with an opposite number in Nic Groom who rarely runs, Kerr-Barlow's bigger impact could come on attack.
The Chiefs' revamped backline features three changes as Rennie's men attempt to rediscover the potency that made them top scorers last season, and Kerr-Barlow was anticipating another tricky test in his side's last home match for a month.
"The Stormers are a very physical side, like most of the South African teams.
"They've got a pretty astute defence structure, so we're going to have to work really hard to try to break them down.
"We've been looking at them throughout the week to see what opportunities there are to exploit, but we're expecting a pretty rough, physical game out there."