Play was stopped, and with Nauga-Grey conscious but unable to be moved, the game was transferred over to the No.2 field, where after a 12 minute wait to take the near-sideline conversion, Thames Valley second-five Kaden Moeke slotted it for 17-5.
Without their talisman player, who was surrounded by concerned helpers while waiting for the ambulance to arrive, and with Thames Valley's big forwards having had a breather, it seemed Whanganui's chances were slim, having been outplayed for the majority of the fixture.
But, fired up by what had happened, Whanganui were like a different team on the opposite field – as they transferred the ball from sideline to sideline, with passes starting to stick better, while they tackled strongly up the middle.
Reserve outside back Anahera Hamahona, who came up from the Whanganui Under 18's, got outside her marker and sprinted through to score, with fullback Shanice Campbell adding the crucial extras.
Reserve prop Waimarie Rauhina started running over tacklers, while halfback Riana Tamati probed for openings as Thames Valley's big girls were beginning to run out of puff.
With the clock running down, Whanganui got a close range penalty to take the tap for Rauhina to bulldoze her way across, as Campbell again landed the clutch conversion, and their team kept Thames Valley locked down midfield to run out the clock.
In the first half the visitors got away to a flyer, as centre Hinemoana Collier dashed through to score after good leadup from her forwards following Whanganui losing the kickoff.
They followed up with a succession of breakdown penalties, as Whanganui infringed in reaching for grounded balls, and after pounding up at the tryline, the defenders were pulled in and the ball was sent wide for Wharepapa to have a free run in.
Right before halftime, Whanganui gave themselves some hope after having few opportunities, with Campbell putting down and recovering her grubber kick, and after sustained build-up on the line, first-five Maze Koro fired a long pass out for winger Paris Munro to score in the corner.
Although he stayed with Nauga-Grey and so did not see much of Whanganui's incredible late comeback, coach Jason Liddle was very proud.
"The first half was very difficult - we started slow, although we scored a try in the last 10 minutes.
"We talked at halftime about just getting back to our game-plan, and rather than panicking, we've just got to make things happen.
"Started to turn it, unfortunately we got an injury, had to switch fields, and the ladies really picked it up to win the game in the dying minutes.
"We'll just keep building on from here."
Nauga-Grey was beginning to get feeling back in her limbs as the ambulance arrived, being transferred to Christchurch in the early evening.
UNDER 18
Whanganui Under 18 blew Thames Valley U18 off the park in the girls' double-header, scoring 11 tries in the 61-0 shutout.
Flanker Hayley Gabriel was virtually unstoppable, ultimately scoring five tries, including the opener, after clearing cover tacklers on her dash down the touchline.
Prop Tamelia Blackburn was the next to charge through under the posts.
Rauhina came on and made a great run before offloading to lock Maina Gray
to score, then from the kickoff Gabriel again sliced through, dragging the last tackler over the line, before making it a hat-trick shortly afterwards off another slicing run.
Whanganui then had to absorb some rare pressure on their tryline, but held out until halftime for 25-0.
More and more gaps began to open in the second half as reserve Kaya Brooks scored off an attacking scrum, and once again from the kickoff, Gabriel took off to dash under the posts.
Whanganui had tried three kickers with no success, but when flanker Samara Pahl-Long broke free to run behind the posts and score, she finally added two points for a big smile at 42-0.
Centre Diaz Gabriel got in on the action with her own breakaway to score between the sticks, Pahl-Long again converting, and then build-up from the set piece had Hayley Gabriel again diving through under the posts for her quintuple and another straightforward kick.
Whanganui still weren't done with Blackburn, breaking through and dragging a despairing tackler the last five metres to get the try on fulltime.
UNDER 15
The Whanganui Under 15's had a tougher test, but ultimately wore down Thames Valley U15 in the second half to blow out to a 43-10 victory.
The visitors showed good control and recycle to score the opening unconverted try, before the home side got a tap near the line for prop Jordi Aleke to just be held up, with skipper and No.8 Elizabeth Adrole taking the pickup to score, and halfback Hannah Byam bringing her kicking boots for 7-5.
Whanganui had bigger forwards than their older Under 18 counterparts, and from a 5m scrum, they carried to the line for hooker Lasaini Aleke to twist through the defence and ground the ball under the pile.
Thames Valley climbed back into it, piggy-backing off a couple of penalties to reach the line and close the gap to 12-10 at halftime; Whanganui's chances not helped by a yellow card for a professional foul.
Far from going into their shells, Whanganui scored back-to-back tries with 14 players after the break, first from one of the reserve players going over in the corner, then Adrole received a quick tap pass near the line and couldn't be stopped for 22-10.
Whanganui liked that move so much they replayed it – Adrole running in a hat-trick after another quick tap, with Byam adding the extras.
An attacking scrum and Adrole was off the back to power over for her fourth try; then Lasaini Aleke capped a memorable game with her own double, Byam adding her fourth conversion.
Around the grounds
DEVELOPMENT XV
The McFall Fuel Development XV made it two wins on the trot after withstanding a second-half comeback from Central Hawke's Bay, winning 21-18 in their away game on Saturday.
SCHOOL
The MRU Secondary School Girls competition saw Whanganui High School and Cullinane College go to a 22-22 draw on Wednesday. In Saturday's Premier 2 (Section A), the Palmerston North Boys High Colts got a 17-15 win over City College 1st XV. Whanganui Collegiate 2nd XV picked up a default win over Cullinane College.
In Youth 3, Whanganui Collegiate went to a 19-19 draw with PNBHS Junior 7.
CYCLONES
The Manawatu Cyclones, with their Whanganui expatriates Mia Maraku and Hollyrae Mete, lost 36-19 to an undefeated Canterbury in Christchurch in their last Farah Palmer Cup round-robin game on Saturday, leaving them bottom of the Premiership table with a 1-5 record.
PEROFETA
Taranaki certainly welcomed back expat Whanganui player and All Black wider squad member Stephen Perofeta for their Bunnings Warehouse NPC clash with Canterbury in New Plymouth on Saturday.
At fullback, Perofeta slotted three penalties and a conversion in the 16-10 upset win.
Fellow expats Vereniki Tikoisolomone and Adam Lennox were on the wing and bench respectively.
