Andy Roddick overcame Mario Ancic 4-6 6-2 6-1 6-4 to level the USA's Davis Cup World Group first-round tie against Croatia on Friday.
DAVIS CUP WORLD GROUP
Slovakia 2-0 Spain
Switzerland 0-2 Netherlands
Australia 2-0 Austria
Argentina 2-0 Czech Republic
Russia 1-1 Chile
France 1-1 Sweden
Romania 1-1 Belarus
USA 1-1 Croatia
The USA fell behind in the tie after Andre Agassi - making his Davis Cup return after a five-year absence - lost in straight sets to Ivan Ljubicic.
But Roddick fought back to outclass Ancic, and the world number three paid tribute to Agassi.
"Andre's far too professional to sit around and let it affect us," he said.
"The whole point of team competition is to pick someone up.
"I'm going to screw up sometimes and I'm going to be able to help out sometimes. We're in this together."
Agassi's return to Davis Cup tennis did not go to plan as he lost 6-3 7-6 (7-0) 6-3.
"I played a great match - everything was going my way," said Ljubicic.
Ljubicic's big serve laid the foundations for his surprise victory, although the turning point of the match came in the second set when he recovered from 5-2 down.
Agassi admitted he was unhappy with his performance.
"I just never settled in - I got what I deserved out there," he said.
"I was pretty uncomfortable. His shots were bouncing pretty aggressively off the court. The wind wasn't very predictable."
Davis Cup holders Spain must win the remaining three matches against Slovakia if they are to avoid a first-round exit from the World Group.
The Spaniards had already expressed their concerns about the fast indoor carpet surface in Bratislava.
And they proved correct as they lost both Friday's opening singles.
Feliciano Lopez was beaten 4-6 5-7 3-6 by Karol Beck while Fernando Verdasco lost 3-6 4-6 7-6 (9-7) 3-6 to Dominik Hrbaty in two hours 43 minutes.
Slovakia's Karol Beck celebrates his win over Feliciano Lopez
"I served and returned really well," said Beck. "But I must admit that I expected a tougher battle."
Spanish captain Jordi Arrese said the surface had been the main reason why he had left Rafael Nadal out of the singles ties.
Elsewhere in the World Group, Lleyton Hewitt and Wayne Arthurs gave Australia a commanding 2-0 lead against Austria with clinical wins.
Hewitt was playing his first match since the Australian Open final but looked in control on grass against Alexander Peya as he won 6-2 6-3 6-4.
And in-form Arthurs followed that up with a 7-6 6-2 6-4 defeat of Austrian number one Jurgen Melzer.
Arthurs and Todd Woodbridge play Peya and Julian Knowle in the doubles.
"It was never easy coming out and playing a Davis Cup match first-up," said Hewitt.
"I knew I wanted to get an early win and take some of the pressure off Wayne in the second match."
In other first-round action, France and Sweden ended the day level at 1-1.
France's Paul-Henri Mathieu took advantage of Joachim Johansson's discomfort on clay to take the opening rubber 6-3 6-4 6-2.
But Sweden hit back when former Australian Open champion Thomas Johansson beat France's number one Sebastian Grosjean 6-4 6-4 7-6 (7-1).
The injury-prone Grosjean was playing his first Davis Cup match since 2003.
In Moscow, Australian Open champion Marat Safin got Russia back on track against Chile.
Safin battled past Adrian Garcia 6-1 3-6 6-3 7-6 (7-4) after Chilean number one Fernando Gonzalez had earlier beaten Mikhail Youzhny 7-6 (7-4) 5-7 6-3 7-6 (7-4).
And Argentina led the Czech Republic 2-0 in Buenos Aires after David Nalbandian and Guillermo Coria claimed four-set wins over Jiri Novak and Tomas Berdych.