Jannik Sinner inspired reigning champions Italy to a comeback victory over Argentina which set up a Davis Cup semi-final against Australia.
World number one Sinner kept Italy in contention after Lorenzo Musetti's loss to Francisco Cerundolo with a commanding straight-set win over Sebastian Baez.
The 23-year-old then partnered Matteo Berrettini to a 6-4 7-5 victory against Andres Molteni and Maximo Gonzalez in the deciding doubles match to complete the turnaround in Malaga.
In a repeat of last year's title decider, Italy face Australia for a place in Sunday's final after they beat the United States 2-1 earlier on Thursday.
Seeking to complete an outstanding individual season by helping Italy retain the Davis Cup, Sinner broke Baez's serve twice in both sets in a straightforward win.
The in-form Sinner won the ATP Finals title on Sunday to cap a year in which he also won the first two Grand Slam titles of his career, however he has also been embroiled in an ongoing doping controversy.
World number 30 Cerundolo produced an outstanding performance to give Argentina the perfect start, closing out a 6-4 6-1 win over 17th-ranked Musetti by winning 12 of the last 15 games after suffering an early break.
But Sinner, who only arrived in Spain on Tuesday - two days after triumphing in Turin - returned following his singles victory to partner the excellent Berrettini and maintain Italy's hopes of winning back-to-back titles.
"The court is very fast and I haven't had much time to adapt, but the most important thing was to keep Italy alive," said Sinner.
Italy captain Filippo Volandri, speaking about Sinner's contribution, said: "He never practised on this court since he arrived. Within three minutes [of his singles match] he was perfectly comfortable. He is a special one."
Italy are seeking to become only the sixth nation to retain the Davis Cup since the final stage was introduced 52 years ago, and first since the Czech Republic in 2013.
Germany beat Canada on Wednesday to confirm a semi-final against the Netherlands on Friday, who knocked out Spain in the final tournament of Rafael Nadal's career.