No other batsman exceeded 10 runs after that as Wanganui were dismissed for 145.
Veteran Dion Ebrahim's crucial 69 then proved pivotal when Taranaki were in a spot of trouble at 70-4 having lost key openers Dean Robinson and Peter Ingram, while medium pacer Hayden McIntyre picked up four prime wickets from Wanganui's deflating second innings.
Rayner was disappointed that despite their start with the bat and some competitive bowling against a strong Taranaki batting lineup, it all came undone so abruptly either side of the lunchbreak yesterday.
"The shot selection was a bit off today and the guys didn't apply themselves," he said.
"They all sort of went out there with the wrong intent.
"Had all intentions of batting for a long time, but the mental toughness of the boys just caved in."
Perhaps playing for time far too early, the batsmen did not make enough attacking strokes to keep the runs flowing which meant the Taranaki bowlers, who were sharp but not infallible, could dictate terms.
"We got bogged down, at one point 20-odd for six," said Rayner.
The problems will be worked over at the Wednesday training session, as Rayner hopes the rescheduled draw where they play three consecutive weekend Hawke Cup games means the team will adapt to the rigours of playing these first-class matchups.
"We know every week, we've got 120 overs of cricket each for two days."
"We've got three guys coming back next week that will be up for selection Mark Fraser, Max Carroll, and Dan Gordon there will be changes."
Taranaki won the toss on Saturday to give paceman Jamie Watkins first crack at Wanganui's lineup, and while openers Brett Cameron and Morgan Inness fell early, Collier dug his heels in while Grant began to play some cultured shots, although he was left sore by a Scott Davidson beamer to his arm.
Grant peppered a couple of sixes into the carpark while Collier also found the middle of the bat but was frustrated by diving Taranaki fielders saving a number of potential boundaries.
At 112-2 and with both in sight of their 50s, the pair holed out with poor strokes off Thomas's bowling, and the rot set in with the final six wickets tumbling for 33.
Rayner was unlucky when Watkins leapt full extension to haul in a great caught and bowled, while Wanganui felt Dominic Lock was hard done by to be given out caught behind, claiming the ball hit his arm.
In reply, O'Callaghan had a great start by pitching up to induce edges from both Ingram and newcomer Trent McGrath, while Hemi got Dean Robinson in the same manner.
From 27-3, Ebrahim started the fightback as Moritz Hartman (29), Thomas (30) and then Watkins (46) all blasted some priceless runs before Nick Blundell cleaned up the Taranaki tail. But when Cameron and Collier fell off McIntyre's bowling, then Thomas ripped through the middle order of Lock and John Macilraith, it all went wrong in Wanganui's second innings.