Needing a strong spinner themselves, Wanganui had to rely on Hadleigh O'Leary (2-85) to send down a lot of overs, while Connor O'Leary tried to extract something out of the pitch with his aggression, only to find the Taranaki batsmen set and comfortable with the bounce.
Sebastian Lauderdale-Smith (53) and Dean Robinson (78) holed out offering up catches to Levi Woolston off the bowling of Hadleigh O'Leary.
But Bailey Wisnewski (100 not out) carried on his merry way with Watson (56 not out), hitting 21 boundaries between them, for Taranaki to raise 321-4 declared in less than 80 overs.
Needing to bat around six hours or score 196 to put their opposition back in again and secure the draw, Wanganui could now just play for time and Chris Stewart (42) and the O'Leary's – Hadleigh (27) and Shaun (19) – were doing so, but wickets still fell to Taranaki's other veteran spinner Liam Muggeridge (3-52), playing his 50th game.
With the top order gone at 114-4 and some 25 overs left in the day to reach 6.45pm, Wanganui were saved by Mark Fraser (46 not out) facing down 126 balls, getting support from McIlraith (34 from 38) who still played shots to break up the spinners rhythm.
Both men also saw off pace bowler Shay Smith, who fired in a succession of short-pitched deliveries that he hoped to unsettle them with.
McIlraith was then bowled by the other Taranaki spinner in Michael Blanks, but the rescue act was all but done as his last boundary put Wanganui back in front, while the visitors bowled the final over restrictively to deny Fraser a deserved 50, with play waved off at 6.32pm.
"It seems we're developing a little bit of a theme where we continue to be a Sunday batting team rather than a Saturday batting team," said Sharrock.
"I think we need to be a little bit more positive when we're batting, looking to rotate the strike.
"In general, we're facing a lot of balls for not many and we need to be trying to be more positive in taking those singles instead of just waiting for four-balls and blocking out the rest."
Thomas had exploited that on Saturday.
"We know what we expect with Mattie - that he varies his pace a lot, and then he typically hits the same spot, so guys have to be pretty switched on to score runs off him, he doesn't give you many bad balls," said Sharrock.
"So it's about being positive and trying to manipulate the length a little bit, try to move the fielders around so we can take those ones and make him think and change his game a little bit, so then that bad ball might come."
The skipper urged patience in Wanganui's results so far this campaign - the team having set long term goals for their rebuild, by getting use out of the indoor centre while finally playing red ball club cricket again through the Coastal Challenge.
"The signs are there, and a bit more time, and next season and the season after we've got enough young guys in this team that given a bit more time in there with the right coaching structure, it's only a good sign."
Wingnut Trophy
The Wingnut Trophy came back up the road from Centennial Park to Whanganui as Treadwell Gordon United Second XI defeated Matt Burke Engineering Marton Saracens by two wickets in the third round of the Rep Weekend Pro40 on Saturday.
The Wanganui United club continues to lead both pools with Property Brokers United First XI on top, having picked up a win over Whanganui Collegiate Senior Blue at the school grounds.
Results, November 27
Rep Weekend Pro 40, Round 3
Pool 1
Whanganui Collegiate Senior Black 83 (A Coelho 3-18, S Sreekumar 3-26, V Chacko 2-4) lost to Wicket Warriors Whanganui 85-3 (Sabari RJ 35no) by seven wickets.
Matt Burke Engineering Marton Saracens 90 (T Westwood 26; L Singh 3-28, L Hoekstra 2-2, K Watson 2-15) lost to Treadwell Gordon United Second XI 94-8 (K Bremer 27; L McAleese 3-17, D Rayner 2-15, F Lane 2-28) by two wickets.
Bye: Wanganui Vet Services Marist
Pool 2
Wanganui United Thirds 60 (S Puli 20; R Moore 5-9) lost to Wanganui Renegades 65-3 (J Donaldson 30) by seven wickets.
Whanganui Collegiate Senior Blue lost to Property Brokers United First XI (scoreboard not available)
Bye: Tech College Old Boys