Argentine substitute Leonardo Mayer denied holders Britain a second straight Davis Cup final appearance with a 4-6, 6-3, 6-2, 6-4 defeat of Dan Evans, clinching a 3-2 upset win on Sunday in the World Group semi-finals.
World number 114 Mayer, now the winner of his last nine Davis Cup singles ties, came good for the visitors after ironman Andy Murray levelled at 2-2 while running on fumes as he as he kept Britain in the chase 6-3, 6-2, 6-3 over Guido Pella. Evans was no match for Mayer who handed the Briton a 12th Davis Cup loss in two and three-quarter hours.
"I am very emotional. I haven't been able to play because of (shoulder) injury so I am delighted to be back on form," the Mayer said. "I don't know what it is about the Davis Cup it brings out the best in me."
Mayer, substituting for Juan Martin del Potro - out of gas after logging more than 10 hours on court from singles and doubles - likely could have gone further after winning the longest ever Davis Cup singles match in 2015 in six hours and 43 minutes.
"I am very proud of all these players, the ones who aren't here, the coaches," Argentine skipper Daniel Orsanic said. "Leo has played very good Davis Cup matches before. He has that feeling in his body and even though he is out of the top 100 that is not his level.
"He was a little nervous in the first set but when he found his rhythm he was on top all of the time.
"We had to keep it to ourselves until the last moment so Great Britain were thinking a little bit but we knew from last night that Mayer would play. I believe it will be an honour to play another final but today we will celebrate a semi-final victory." Murray lost in opening singles to Del Potro but teamed up with his brother to give Britain the doubles point.
The Argentines will travel to Croatia for the November 25-27 final after Marin Cilic assured his side of only its second final appearance.
The former US Open winner clinched the victory as he thrashed Richard Gasquet of France 6-3, 6-2, 7-5, hammering 14 aces and producing 21 winners.
France's Lucas Pouille then defeated Marin Draganja in the dead fifth rubber to make the winning score 3-2.
"When you look at the atmosphere, it’s an incredible feeling. It’s been a dream weekend for us," Cilic said. "I played incredible tennis. I produced a great performance for all the crowd. I can’t be more proud than right now. "We have always been playing well in Davis Cup. It’s something that’s in your heart. It was a tough tie but this wonderful crowd inspired us.
"We can now look forward to what should be a great final."
Croatia made its only other appearance in the title match in 2005, when Ivan Ljubicic - now coach of Roger Federer - led his nation past Slovakia in Bratislava.
"We played so many ties away, we had been waiting to play at home and now we just won in front of our home crowd it's amazing," Croatia captain Zeljko Krajan said. "Marin was our leader all the way, he won everything despite the pressure that was on his shoulders."