With Croatia missing Marin Cilic and Borna Coric, doubles specialist Nikola Mektic had to play singles against Roberto Bautista Agut, losing 6-1 6-3.

Nadal then beat Borna Gojo 6-4 6-3.

Meanwhile, Serbia, who won the Davis Cup in 2010, put themselves in pole position in Group A with a 3-0 victory over Japan at the Madrid event.

Filip Krajinovic defeated Yuichi Sugita 6-2 6-4, Novak Djokovic thrashed Yoshihito Nishioka 6-1 6-2, and Janko Tipsarevic and Viktor Troicki clinched a tight doubles match against Ben McLachlan and Yasutaka Uchiyama, winning 7-6 (7-5) 7-6 (7-4).

Germany also triumphed 3-0 as they defeated Argentina. Philipp Kohlschreiber battled back from a set down to defeat Guido Pella 1-6 6-3 6-4 and Jan-Lennard Struff was too good for Diego Schwartzman with a 6-3 7-6 (10-8) success.

In the doubles, the German pairing of Kevin Krawietz and Andreas Mies overcame Maximo Gonzalez and Leonardo Maye after the longest tie-break in Davis Cup history as they won 6-7 (4-7) 7-6 (7-2) 7-6 (20-18).

Great Britain's near nine-hour tie with the Netherlands,which ended in a 2-1 victory for GB, meant that the tie between Australia and Belgium to decide who will win Group D started two hours later than scheduled.

Spain's victory over Russia on Tuesday had finished in the early hours of Wednesday and a similarly late finish looked on the cards for both Australia v Belgium and the Group F match between the United States and Italy as questions over scheduling arose at the re-vamped competition.

The United States were at the centre of controversy after group winners Canada conceded their doubles rubber on Tuesday when they had an unassailable 2-0 lead.

It meant the US were given a 6-0 6-0 win for the doubles, which could potentially help them qualify for the last eight as one of the two best runners-up.

Organisers the ITF said three Canadian players had been declared unfit to play, but Britain's Andy Murray was among critics of the decision to forfeit, saying: "I don't think that's good.

"So where Canada may have felt that that was a dead rubber in theory for them because they were already through, that could have implications to all of the teams potentially that might finish in second place."