Harding turned out for Marist last Saturday, however Marr said he will not yet be conditioned enough for bowling in the two-day format.
"I'm not going to get 15 overs out of him."
Therefore, youngsters Connor O'Leary and Angus Dinwiddie, who both debuted last season, will form the core of the pace attack with veteran Ross Kinnerley.
While logic would dictate Kinnerley takes the new ball, Marr has given Badger carte blanche to think outside the box with his bowler rotations, perhaps starting with the teenagers or someone else.
"He's got a good cricket brain and he's the one who makes the decisions on the field."
With Inness not taking the gloves, Marr has brought back a blast from the past as Manawatu's Bryce Grant, who captained Wanganui in 2013-14, returns as an import player.
The big blow is while Canada's Akash Gill arrived back in Whanganui this week, NZ Cricket have handed down the mandate that the team already have their one allowed overseas player in leading batsman Greg Smith.
The Englishman Smith, who captained Wanganui twice last season, has now been living and playing in the district for more than three years - while both men played in the same team last summer.
"NZ Cricket have put the kibosh on [Gill's] eligibility," said Marr.
Decisions will have to be made in the future whether to rotate the two men, or stick with Smith unless there is an injury or loss of form.
Last minute dramas aside, Marr is hoping to build on last summer's strong showing in the Hawke Cup, including against Taranaki.
At Pukekura Park in New Plymouth, rain washed out the first day of play, and then Wanganui batted 80 overs on a pace bowler's paradise to be all out for 178.
They nearly stole a first innings points victory, as Taranaki just reached 182/7 off the second-to-last delivery of the game. "We believe that we have to have confidence," Marr said.
"Man for man ... Wanganui have got just as good a skill level. It's who plays their best cricket on the day."
Unlike last November, however, Wanganui must be prepared to be at their best for session after session, because the weather is likely to allow two full days' play.
"[The pitch] played pretty well last week. I think it's a bit harder, bit more pace and bounce," said Marr.
Taranaki's team includes a couple of names to watch for - pace bowler Ryan Watson and former Black Cap Peter Ingram.
Ingram is making something of a surprise comeback to minor representative cricket at age 39, however with 274 runs from three 50-over club games, he made it easy for coach Debu Banik to grant his request for inclusion.
Watson took 29 wickets last season and has previously taken six and seven wicket hauls in an innings against Wanganui at Victoria Park, the last time leading to a 10-wicket win in 2015.
Play starts at 11am tomorrow. In the other games, Manawatu face Horowhenua-Kapiti in Palmerston North and Wairarapa host champions Hawke's Bay in Masterton.
The teams
Taranaki
Peter Ingram, Dean Robinson, Ryan Fleming, James McDougall, Kaylum Boshier, Liam Muggeridge, Moriz Hartmann, Phil Barraclough, Ryan Watson, Mattie Thomas, Callum Stuart, Shay Smith-Lound.
Wanganui
Simon Badger (c), Greg Smith, Thomas Walshe, Trey Bidois, Mark Fraser, John McIlraith, Matthew Simes, Bryce Grant (wc), Ross Kinnerley, Connor O'Leary, Angus Dinwiddie, Chris Stewart.
