Wairarapa Bush, who due to previous defeats were out of contention for the Shield final, ultimately scored six tries but only landed one conversion, or else they would have surpassed Wanganui's total sooner.
Paddy Gluck got a double for the home side.
McCrea said the Wanganui scrum was solid in the first half, but after the break they followed standard procedure and made a lot of changes, which when coupled with the sinbinnings saw the team lose their shape.
Instrumental second-five Troy Brown was already unavailable and when his midfield partner Josiah Bogileka came off with a rolled ankle, Wanganui had lost their attacking punch.
Bogileka had been a standout, as was Bryn Hudson in his return to No 8, along with outside back Samu Kubunavanua.
McCrea agreed the rotation tactics will likely have to stop for the final with Wellington Maori Development, who defeated Horowhenua-Kapiti on Saturday to book the other spot in the Shield game.
"We've got some hard decisions to make, obviously we'll be picking the strongest team to start."
Wanganui Development comfortably beat Wellington Maori Development 49-22 at City College on August 25, when the visitors were short of players and borrowed four reserves from the home side.
However, being closer to home base with the final hosted in Levin and having won their last two matches, McCrea is expecting the Maori to be reinforced and much stronger this Saturday.
"They will be, I've no doubt about it. We are going to have to be a lot better than we were yesterday [Saturday]."
Another cause of concern for McCrea was his player's health after many of them were "grazed up" by the artificial turf at Masterton.
Laid in 2015, there have been several issues with players getting infections from cuts and scratches on the all-weather turf, which allegedly includes Steelform Wanganui captain Campbell Hart who missed a Mitre 10 Heartland championship match due to his knee.
"You wouldn't believe it," said McCrea.
"I don't know how much iodine, vaseline, and tape we used.
"It's no secret, something's got to be done."
* * * *
It was a better weekend for the Air Chathams Wanganui Under 18 squad, who got their competition underway in earnest with a 32-0 shut out of East Coast U18 at Whakarua Park in Ruatoria on Saturday.
Wanganui came into the match on the back of two preseason losses, but even after bussing nearly two hours up the coast following the direct morning flight to Gisborne, the team still delivered in very wet conditions.
Their next game is a home fixture against Wellington Samoan U18 at Cooks Gardens on Saturday.
