Nonu will travel with the Blues to South Africa for their matches against the Bulls and the Stormers following Friday night's game against the Chiefs in Hamilton.
Lam will be grateful for his presence in the midfield - probably alongside Benson Stanley - in what will be two challenging encounters in Pretoria and Cape Town.
He would probably prefer Nonu to be available to join Stanley against the Chiefs' pairing of Sonny Bill Williams and Richard Kahui, but the man himself reckoned the Blues will do okay without him.
"They've seen the way they play. [They have] big ball runners and Sonny can do a lot of things. Kahui, as well, he defended well last week. I think he's the best defender in New Zealand along with Conrad [Smith]. The boys are up to it and we're looking forward to the game."
The nerves he felt travelling to watch the Blues play the Crusaders at Eden Park last weekend were a good sign, he said.
"It's good in terms of being in a place where I'm unsure what's going to happen. [I'm] nervous at the same time and a little scared because I haven't settled into Auckland. I remember driving up to the game on Friday. Normally I'd be on the Hurricanes bus and feeling the nerves or the butterflies. But I'm nervous in a different way joining the Blues team. I'm looking forward to it."
The Blues will be without tighthead prop Charlie Faumuina after he injured medial ligaments in a knee during a training session on Monday but Lam said it wasn't a major problem and the tighthead prop should be available for the South Africa trip.
"Charlie is our number one tighthead at this stage and on the back of Tony Woodcock not being available, it's a big hit for us," Lam said.
Angus Ta'avao is on the bench as prop cover and, in the only other change to the Blues line up, Gareth Anscombe comes on to the bench ahead of Hadleigh Parkes.
While Lam was disappointed to lose Faumuina, his injury worries can't compare to the Chiefs after props Ben Afeaki and Toby Smith, halfback Brendon Leonard and wing Lelia Masaga limped off against the Highlanders.
Big prop Ben Tameifuna, a 20-year-old who weighs 138kg, is one beneficiary. Tameifuna, a cousin of loosehead Sona Taumalolo, was a member of the New Zealand Under-20 Junior World Championship side last year and will be making his debut.
"The injuries have meant there has been some movement in the team, but it also provides a great opportunity for the young guys to make their debut," said Rennie.
Chiefs: Sona Taumalolo, Mahonri Schwalger, Ben Tameifuna, Craig Clarke, Brodie Retallick, Liam Messam, Tanerau Latimer, Kane Thompson, Tawera Kerr-Barlow, Aaron Cruden, Tim Nanai-Williams, Sonny Bill Williams, Richard Kahui, Asaeli Tikoirotuma, Robbie Robinson, Hika Elliot, Shane Cleaver, Fritz Lee, Sam Cane, Augustine Pulu, Andrew Horrell, Declan O'Donnell.
Blues: Tom McCartney, Keven Mealamu (c), Tevita Mailau, Anthony Boric, Ali Williams, Chris Lowrey, Daniel Braid, Jerome Kaino, Alby Mathewson, Michael Hobbs, Rudi Wulf, Benson Stanley, Rene Ranger, David Raikuna, Isaia Toeava, Pauliasi Manu, Angus Ta'avao, Brad Mika, Luke Braid, Piri Weepu, Gareth Anscombe, Sherwin Stowers.
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