The United States made light of the absence of several top singles players as they began their Davis Cup Finals group stage campaign with victory over Chile on Wednesday.
Reilly Opelka and Brandon Nakashima both came through lengthy three-set battles to give their team a winning lead in the Group C opener in Zhuhai, China.
Olympic doubles silver-medallists Rajeev Ram and Austin Krajicek then beat Matias Soto and Tomas Barrios Vera to wrap up a 3-0 victory and join Germany at the top of the table.
Defending champions Italy were without world No 1 and newly-crowned US Open champion Jannik Sinner but made a positive start as they took a winning lead against Brazil in their opening Group A tie in Bologna.
Spain boasted Carlos Alcaraz in their ranks but the world No 3 was given a scare against Czech Republic's Tomas Machac, losing the first set tiebreak before winning the second set 6-1 at which point Machac was forced to retire to hand Spain an unassailable 2-0 lead in Group B in Valencia. Roberto Bautista-Agut had earlier beaten Jiri Lehecka 7-6(1) 6-4.
American captain Bob Bryan was unable to call upon the likes of US Open runner-up Taylor Fritz, Frances Tiafoe or Tommy Paul but his team showed its strength in depth.
Opelka, ranked 309th in the world after wrist surgery, beat 116th-ranked Cristian Garin 6-3 4-6 7-6(3) before Nakashima, the world number 40, beat Alejandro Tabilo 7-6(5) 2-6 7-6(3).
Ram and Krajicek also needed three sets in the doubles to give 32-time Davis Cup winners the US the perfect start as they bid to reach the last eight for the second time since the new format was introduced in 2019.
"It was truly an epic day of tennis for both teams," Bryan said. "Everyone showed a lot of heart, a lot of guts. Hats off to the Chileans."
Four groups of four nations are being contested in four different cities – Zhuhai, Bologna, Valencia and Manchester – with the top two from each group progressing to the final eight-nation knockout round in Malaga in November.
Italy's Matteo Berrettini beat Brazil's Joao Fonseca 6-1 7-6(5) to give his side a flying start and Matteo Arnaldi then outlasted Thiago Monteiro 7-5 6-7(4) 7-6(5) in a match lasting three hours and 39 minutes to put the hosts into a 2-0 lead.
Britain also had home advantage as they took on Finland in their Group D clash in Manchester and made it count with debutant Billy Harris sealing victory after Dan Evans had begun proceedings with a win over Eoro Vasa.
Harris, given his chance in the absence of British No 1 Jack Draper, beat Otto Virtanen 6-4 7-6(4).
Finland did win the doubles as Harri Heliovaara and Virtanen beat Evans and Neal Skupski.
Australia beat France in Group B on Tuesday while Germany beat Slovakia in Group C, Belgium beat the Netherlands in Group A and Canada were victorious against Argentina in Group D.