A "gutted" Warren Gatland felt his Wales side had been made to pay for their naivety as they suffered a 14-12 defeat to Australia in Cardiff.
Four penalties from Leigh Halfpenny, who was carried off on a stretcher at the end of the game and has gone to hospital for scans on his neck, looked to have given Wales victory over the Wallabies as they led 12-9 with time running out.
But Kurtley Beale, who scored all Australia's points, raced onto a Dave Dennis pass to cross in the corner with just 26 seconds remaining.
Halfpenny suffered his injury in the build-up to the score, taking a heavy hit as he attempted to halt Dennis.
Wales lost to the Wallabies in similar fashion in the second and third Tests of their 3-0 summer series defeat Down Under, and Gatland, who now leaves the Welsh set-up to focus on his Lions duties, admitted a repeat was hard to take.
"We are pretty gutted," he said. "I thought apart from the last minute, we played some outstanding rugby today.
"It was a close, tight Test match, which you expect. We put ourselves in a position where we should have won."
And the New Zealander accepted his side had only themselves to blame for this latest reverse - Wales' seventh in a row.
He said: "The disappointing thing for me is we turned over a line-out and it was obvious Australia were going to run the ball from behind the goal-line and we allowed them to get 30 metres from that and release a bit of pressure. We should have had guys in the front line and defended that a bit better.
"Also in the last couple of plays we had people hanging back so it was a bit of naivety. It was a tough match and it was disappointing.
"We haven't spoken to the players yet but I would want to know what was our communication at the last scrum. They were set up to move the ball and we had to make sure they did not get out of their 22.
"I am not sure we communicated or spoke but until I speak to the players I am not sure."
Crestfallen captain Sam Warburton added: "We kept them out for the whole game and defended reasonably well, and it is probably the hardest defeat I have had to take as a player.
"I was gutted when I looked up and saw the break and saw Kurtley Beale going for the line. You knew that was it, really.
"It was demoralising because the effort was there from everybody and it felt like today was the day we were definitely going to do it."
Defeat means Wales will drop into the third group of seeds for Monday's 2015 World Cup draw, which is almost certain to leave them with a hazardous pool to negotiate when the tournament comes around.
There is also the small matter of an RBS 6 Nations title defence looming on the horizon, with a squad short on confidence after a miserable autumn.
But Gatland said: "Even if we had won today we would have been disappointed after dropping a couple of games (against Argentina and Samoa).
"But in the second half last week and today we played some good rugby and showed we are a good side - we just need to be smarter at the death.
"That's a few times that's happened against Australia where we have not been able to finish them off and we need to be more clinical."
Australia coach Robbie Deans praised his side's character as they rounded off a 15-Test season on a winning note.
He said: "It was a great game as all of our encounters with Wales have been this year.
"It was a great Test match to finish the year on, it had everything.
"Credit to the lads for even being in the game at the end, they have had a huge year and that was a fast and physical game so to be in the game at the end was credit to them, but to get up to win it was even better."
The game also marked the 116th and last Test appearance for Wallabies captain Nathan Sharpe.
And a visibly emotional Sharpe admitted he will miss the game he has devoted his life to as his distinguished career comes to a close.
He said: "Of course I will miss it. It's what I have done as long as I can remember.
"I might have to find some walls to run into every weekend to ease my way out of it I think.
"The thing I will miss the most is being in that team environment and having a goal that is in that pressure cooker situation.
"You love it and you hate it, it's big highs and low lows so that will be most challenging thing for me."
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