Marr believes Smith was familiar enough with his bowlers to be able to rotate them effectively.
"There's a lot of experience on the park to help him.
"It's a leadership group - I don't like that term, but that's the way it is."
Having batted for nearly 80 overs in green pitch conditions against Taranaki, which almost saw them through the sole day's play before Taranaki just passed their total with one ball remaining, Marr is hopeful of another collective effort in better conditions this weekend, although he acknowledges this "could be a banana-skin type of game for us".
"There's certainly confidence in the group, and you can see that in the body language.
"It wasn't just one performer [in New Plymouth], it was a group performance.
"It's the team approach to things, [having] that partnership of 60-70.
"We need seven points from this game, that's just the way it is. I don't feel we're underdogs in this."
Of biggest concern coming out of the final Porter Hire Premier 1 round this weekend was the low scores from most of the top orders - notably Marist who had four ducks until Mark Fraser played a sublime innings of 143 not out.
The veteran could not have timed his form better, as that effort recalled his match-winning 99 two seasons ago in the innings win over Wairarapa on the same Tasman Tanning No1 pitch.
"Dogger can do that, we know he can do that. The concern is there is not enough guys doing that," said Marr.
"We say every training, 'you guys need to be doing it at club level'."
Weather predictions of scattered showers could also rob the match of a few sessions, although this could end up being to either team's advantage depending on momentum.
"There's 112 overs in a day, there's a hell of a lot of cricket," said Marr.
One of the coach's biggest concerns is the lack of a quality specialist spin bowler - not such a worry on green pitches, but crucial later in the summer as the grounds dry out.
This proved true in December 2014 when Wanganui last had an outright victory - a big innings and three run win over Wairarapa at Victoria Park.
Dominic Lock (35) and Fraser (99) batted for over four hours to wear out the young Wairarapa bowling attack as part of 270 from 88 overs.
The bowlers in speedster Ryan Slight, spinner Henry Collier and medium pacer Rayner among others then tore Wairarapa apart twice for 115 and 152 to leave them short by the middle of Sunday afternoon.
However, the roles were reversed in February this year down at the Ratheale Oval, as Wairarapa got their revenge with an innings and 56 run win.
After Wanganui's bowlers had the hosts under pressure at 144-6, Paul Lyttle (76) and captain Gordon Reisima (94) got away on them in the final Saturday session to post an imposing 323-8.
Wanganui's top order fell apart twice, with little coming underneath it, as they were dismissed for 121 and 146 in a performance then-coach Stuart Gillespie labelled as "just gutless".
Daniel Ingham and Dean van Venter were the chief destroyers with the ball for Wairarapa, although it was accepted the visiting batsmen helped them with poor shot selections.
Play starts tomorrow and Sunday at 11am.
The Wanganui team is:
John McIlraith, Calum Coker, Dominic Lock, Greg Smith (c), Mark Fraser, Dominic Rayner, Angus Dinwiddie, Nick Harding, Akash Gill, Chris Sharrock, Ross Kinnerley, Todd Inness.
