Calvert had already collected a yellow card, which no-one disputed, when he accidently caught the attacking player while going for the ball in the first half, with Massey slotting the penalty to go 2-0 up at that stage.
"When your goal keeper picks up one yellow card, you don't think about it too much - they're a fairly protected species," said Jason King.
However, with Athletic feeling Symon King was only penalised because of the Massey striker's yell, Calvert lost composure and kicked the ball away, resulting in his second yellow card and an automatic red.
Athletic moved Kelvin Hove into the box and he managed to save the penalty attempt, but with only nine men out in the field the visitors were going to be up against it to score an equaliser.
Nonetheless, they missed several chances, including hitting the cross bar, with the students hanging on for the surprise win.
"We just couldn't put it in the goal. Even with the nine, the guys were fired up," said Jason King.
Massey's goalscorers were Matthew Hilson and the Freeman's - Cole and Joseph.
The double blow of the unexpected defeat and the automatic stand down of Calvert leaves Athletic looking shaky for the trip to Napier.
Jason King's GVCA Wanganui Athletic Reserves squad are already operating with a makeshift keeper, so the coach will look to one of the current 1sts to take the gloves, while promoting another defender.
Symon King, who has experience in the position and was Athletic's goalie in last year's Chatham Cup match, is the likely choice.
"Whoever we move in there leaves a hole," Jason King said.
"That's now a 'me problem' for the rest of the week - to find a [overall] squad that can do it."
It was a tough day for the club as the Reserves lost their Horizons Premiership away game to Feilding United 3-1 at Timona Park, with Sergio Serra getting their sole goal.
