The All Blacks had to fight back to win the first test in Johannesburg and were trailing from the second minute against the Springboks in last Saturday’s second test in Cape Town.
“A big part of our game is our continuity, but we need to really front up as well. Starting quicker would be pretty important,” Rennie told a press conference on Thursday.
“We've put a bit of time into that part of our game. But our big men at the set pieces is crucial as we know and we think we've got a group of guys who’ll work hard around the field and provide opportunities for us."
With the series poised at 1-1, the Kiwi coach made three changes to the pack in a bid to add extra energy and also fix up their struggles with the lineout.
“I said a couple of weeks ago that it's going to take more than 23 guys to win the series here, so it's much about sharing the load,” he said of the axing of veteran hooker Codie Taylor, who is replaced by Asafo Aumua.
“We've made a couple of shifts for the lineout, I won't divulge too much but that we think it will make the task a lot easier.
“As we know, with a lineout there’s got a lot more to do than just the hooker and so we expect to be better there this week,” added Rennie.
The All Blacks are embarking upon their first full tour of South Africa since 1996! Marketed as the 'Greatest Rivalry' series, the winner will come out not only with the bragging rights but World Rugby's number one ranking. Keep up to date throughout August and September with news, previews and more.
All tour fixtures | All tour results | Rugby match previews | Rugby news
In the second row, Sam Darry will play a first test of the series with Fabian Holland dropped to the bench while Josh Lord rests again after suffering concussion in the first test.
“There’s not much between our locks but Josh Lord had his first day back at training today so we decided not to consider him. He's had a bit of a history of concussion and so we're going to err on the side of caution.
“Sam Darry hasn't played in the test series but has a massive engine and that’s how we want to play. That'll be handy at altitude, we think.”
Rennie said he also expected an impact from Peter Lakai who replaces Simon Parker on the side of the scrum.
“He's not a big loose forward compared to maybe some of the other men on the field, especially in the opposition, but he's really physical. He hits in the tackle and clean and then he's a hell of an athlete and so what you lose a little bit in bulk, he'll give us plenty around the track.
"He’s started a couple of other tests this year and he's always fronted when given an opportunity.”