New Zealand begin cut-throat camp
"This is really the last piece of the puzzle," Herbert told reporters as his four-year campaign to get the All Whites back to the World Cup finals entered its last steps.
"We've got a real diverse group, players that will go to the World Cup and some that are challenging," he added at a 12-day camp, which had its first full training session on Thursday.
"We've set the bar extremely high this week and if they haven't come well-equipped for that then they may struggle."
Herbert said the majority of his 23-man squad had already been pencilled in for the June 11-July 11 finals in South Africa, though there were still "four or five spots" available.
"It's all down to performances now, it's really quite simple for them," he said. "We've built a fantastic brand in the group over four years and its real strong and tight.
"But this camp is a little bit diverse and spots are up for grabs. While there is a collective approach going into games it will be cut-throat.
"It's dog eat dog a little bit through the week and I think 'Bring it on!' because that's what we're looking for."
The camp, which is made up of only Australasian-based players, will conclude with a match between an All Whites eleven and a selection from the domestic league, and Herbert also said players in that selection could even force their way in.
"When a tournament of this stature is up for grabs and you want to be part of it and I would be disappointed if I didn't see it," said Herbert, who was a central defender when New Zealand made their only other World Cup appearance in Spain in 1982.
Goalkeeper Mark Paston, who required surgery on a broken leg, and midfielder Jeremy Brockie, who broke his leg and had to have a plate inserted, both took part in training.
"I've had a couple of months now building up training-wise and my knee has been pretty good, so I'm pretty happy with it," said Paston, whose penalty save in the second leg of the Asia/Oceania play-off with Bahrain last November ensured the All Whites qualified for South Africa.
"I've had plenty of time to get some training under my belt for it not to be a problem. It's been hard and sometimes you thing 'am I going to get there?' But week by week you get stronger so I think I'm a lot closer."