Del Porto ties it up for Croatia

Juan Martin del Potro fought off stomach problems and beat Ivo Karlovic on Friday, leaving Argentina tied with Croatia in the Davis Cup quarterfinals.

Del Potro defeated Karlovic 6-2, 7-6 (7), 6-1.

Marin Cilic gave Croatia the lead, beating David Nalbandian 5-7, 6-4, 4-6, 7-6 (2), 6-3 in a match that lasted 5 hours, 9 minutes and put pressure on Del Potro.

Nalbandian and Eduardo Schwank are scheduled to face against Cilic and Lovro Zovko in Saturday's doubles match on the outdoor clay court. Nalbandian said he intended to play despite speculation captain Martin Jaite might replace him with Juan Monaco. Reverse singles are Sunday.

The 23-year-old Cilic wore down the 30-year-old Argentine, finally winning on his third match point.

Isner tops Simon to level U.S. vs. France 1-1

Czechs, Serbia split singles rubbers

Janko Tipsarevic saved three match points to beat Radek Stepanek 5-7, 6-4, 6-4, 4-6, 9-7 Friday, pulling Serbia even with the Czech Republic after the opening singles of their Davis Cup quarterfinal.

Earlier, Tomas Berdych eased past Viktor Troicki 6-2, 6-1, 6-2 to give the Czechs a 1-0 lead on the indoor clay court at O2 Arena.

Tipsarevic, who has climbed to a No. 8 ranking, faced a match point at 5-6 and two more at 6-7 in the fifth set. But he served well to remain in the match and won in more than five hours.

Doubles in the best-of-five series is Saturday and reverse singles is Sunday.

The winner advances to the semifinals in September. Serbia, without top-ranked Novak Djokovic, is looking to make a third straight semifinal.

Spain grabs early lead

Defending champion Spain has taken a 2-0 lead over Austria in the Davis Cup quarterfinals lead after easy victories by Nicolas Almagro and David Ferrer.

Almagro, ranked No. 12, opened the best-of-five series Friday by beating Jurgen Melzer 6-2, 6-2, 6-4 on an outdoor clay court. Ferrer, ranked No. 5, followed by defeating 139th-ranked Andreas Haider-Maurer 6-1, 6-3, 6-1.

Spain, five-time Davis Cup champions, can capture its 23rd straight home victory by winning Saturday's doubles. Marcel Granollers and Marc Lopez will face Alexander Peya and Oliver Marach.

The winner of this series will advance to September's semifinals against France or the United States.

SI Apps
We've Got Apps Too
Get expert analysis, unrivaled access, and the award-winning storytelling only SI can provide - from Peter King, Tom Verducci, Lee Jenkins, Seth Davis, and more - delivered straight to you, along with up-to-the-minute news and live scores.