The 73rd minute try in Saturday night's elimination final in Townsville came off a Jake Clifford bomb. It was knocked back by winger Kyle Feldt, bounced off the knee of second-rower Heilum Luki and was then knocked on by Newcastle's Daniel Saifiti.
From there Cotter went to regather but the ball hit his knee. It was hardly believable at that point. But what was believable was the determination of Cotter as he got to the ball ahead of Knights superstar Kalyn Ponga by a whisker to score.
"I was happy. I think that is a great example of someone who keeps competing until the play has stopped and Reubs has done that his whole career," Cowboys coach Todd Payten said.
Cowboys co-captain Reuben Cotter (r) led by example. (Scott Radford-Chisholm/AAP PHOTOS)
Fellow co-captain Tom Dearden then iced the win with a final try as the Cowboys set up a semi-final clash with Cronulla in Sydney on Friday night.
"There has been a couple of questions about our toughness and we answered that tonight. We are looking forward to going to Sydney next week with a healthy squad," Payten said.
Skipper Ponga inspired the Knights like only he can to give them a 12-4 lead at the halftime break.
His dazzling footwork was on show early before he set up two tries, one with a trademark burst and another with a well-judged bomb.
Knights skipper Kalyn Ponga was at his creative best but it wasn't enough. (Scott Radford-Chisholm/AAP PHOTOS)
His teammates, battle hardened by their three do-or-die regular season matches in the leadup, were resolute in defence and conceded only one first-half try to an intercept.
Veteran Cowboys winger Kyle Feldt scored his 23rd try of the season, a new club record, when he snaffled an errant pass by fill-in centre Dylan Lucas in the 14th minute to race 85m to score.
Earlier, Ponga ghosted his way through a hole from 40m out and found hooker Jayden Brailey with a scintillating pass to give the visitors the lead.
Ponga called centre Dane Gagai to get ready for a lobbed bomb and landed it to perfection. Gagai contested, Cowboys fullback Scott Drinkwater and winger Fletcher Sharpe swooped.
The home crowd was stunned into silence after the Cowboys had 62 per cent of the possession in the opening 40 minutes.
Dearden delivered a try-saving play when he rushed back to tip the ball dead when Knights second-rower Tyson Frizell seemed certain to score.
A brilliant tap-on by Cowboys centre Valentine Holmes for winger Murray Taulagi to score straight after half-time got the Cowboys back in it.
The Cowboys finally grabbed the lead when Drinkwater put prop Jordan McLean over under the sticks but the Knights hit back when Lucas crashed over.
Jordan McLean puts the Cowboys ahead with his try. (Scott Radford-Chisholm/AAP PHOTOS)
Ponga hit the uprights with the conversion, leaving scores level at 16-all and setting up a thrilling final 15 minutes.
Ponga split them and Gagai dropped a low pass with the line open before Cotter's heroics allowed the Cowboys to go clear. Knights prop Leo Thompson was sin-binned at the death for a late hit on Feldt.
"Other than the scoreboard it was a pretty good performance but a pretty s***** way to start (the second half)," Knights coach Adam O'Brien said.
"It is never nice to lose a finals game but over time when we look back at the season we were gritty and tough when there were plenty of things said about us and no-one gave us much of a chance."
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