"I know I need to develop my fitness more if I want to be in the team," Hurrell told the Herald on Sunday, "I'll be pleased if I can have an 80 minute game but I am still not fit enough. I still need a few more games to get used to the speed and the intensity.
"Training makes it easier to adapt, as it can be really hard - just like a game. I also need to work on my defence, in terms of reading the play, wrestling the players and not getting too lazy on the field."
"I feel like we are developing him well," says McClennan. "He will get there [as an 80-minute player] - I just want to manage him along carefully."
To be fair, the 20-year-old has already surpassed expectations in the swift adjustment to the NRL, in just his second full season of league.
Hurrell, who emigrated from Tonga in March 2009, was a revelation in the Toyota Cup in 2011 (22 tries in 21 games) but has managed the step up well and still has only one NRL pre-season behind him.
"Before the game, I feel a bit nervous and some pressure but once I take the first one up, I feel comfortable from there," says Hurrell. "I know [I am targeted sometimes] but I kinda like it; I like running hard back at them too. You need to be ruthless in this game."
Hurrell admits his decision to switch codes (he played for Auckland Grammar 1st XV up until 2010) was difficult.
"It was pretty hard," says Hurrell. "When I grew up in Tonga, all I knew about was union and my goal was to play for the New Zealand team.
"When I came here, I wasn't really keen to move to league but I talked to my parents and they said I was old enough to make my own decision."
"[Former school mate] Omar Slaimankhel told me it was a beautiful environment and he was enjoying every moment of it.
"I thought if I don't make it, then I can always go back to union. But obviously I've got no regrets and I am loving every moment of it."
The presence of Hurrell and other Tongans has also prompted a mini league revolution back in his homeland, with the NRL on television screens there for the first time.
"The NRL is now live back in Tonga," says Hurrell. "When I scored a try against [Parramatta], they almost blew away our house."