By Zoran Milosavljevic
ZAGREB (Reuters) - Argentina fought back to level an absorbing Davis Cup final against hosts Croatia as Juan Martin Del Potro beat Ivo Karlovic 6-4 6-7(6) 6-3 7-5 after Marin Cilic's five-set defeat of Federico Delbonis on Friday.
Neither world number six Cilic nor Argentine Del Potro were originally picked for Saturday's doubles but both teams' talismans are now likely to be called upon for a potentially pivotal contest in what is shaping up to be a knife-edge tie.
Del Potro had to dig deep to overcome Karlovic, who was spurred on by an electrifying atmosphere in the Zagreb Arena.
A raucous home crowd was matched by an equally fervent Argentine contingent, which included the country's former soccer team captain and World Cup winner Diego Maradona in the VIP box.
"It was great to have Diego here, everyone wants to see him and he is a very nice person who likes tennis," Del Potro told a news conference.
"But the most important thing for us is to stay focused. It was an exhausting match but I think I will be OK for the rest of the weekend."
Argentina's coach Daniel Orsanic added: "We haven’t talked about tomorrow yet and we are not keeping any secrets as to who will play in the doubles.
"We have nothing to hide and we will make a decision when we return to the hotel. My educated guess is that Cilic will play alongside Ivan Dodig."
Del Potro broke Karlovic's serve early on and held his own to clinch the opening set but although the Argentine predictably dominated the baseline exchanges, he was powerless against the Croatian's lethal serve as the match wore on.
Karlovic rifled in a flurry of aces to keep nosing ahead in the second set and saved a double break point to clinch the tiebreak, drawing wild cheers from the home fans.
That was as good as it got for the Croatian, however, as Del Potro upped the pace and prevailed in the last two sets, with an exuberant Maradona pumping his fists in delight.
Cilic had fired the hosts ahead by outlasting Delbonis 6-3 7-5 3-6 1-6 6-2 in a titanic tussle, having recovered after losing his momentum when he squandered three break points in the seventh game of the third set.
Cilic rained down a barrage of aces and service winners in the opening set after breaking his opponent's serve in the fourth game to edge ahead.
He broke again in the 11th game of the second set and held serve to take a commanding 2-0 lead before Delbonis hauled himself back into the match.
The Argentine saved three break points in the seventh game of the third set and claimed it with a searing forehand winner.
He could not miss in the fourth, racing through it with a barrage of spectacular shots against a subdued Cilic.
The resurgent Croatian found another gear in the fifth set, breaking Delbonis in the second game and again in the seventh before he sealed the match in three hours and 30 minutes.
Croatia coach Zeljko Krajan was pleased with the opening day's outcome after conceding he had hoped for an upset which would have given his team a commanding 2-0 lead.
"I am satisfied with the result on the opening day, although I hoped we could win both singles," he said.
"Karlovic played some great tennis and it came down to a few points, it cloud have gone the other way.
"The pressure on all players was enormous and under such circumstances I didn’t expect Cilic to shine throughout the contest. But the most important thing is that he came out on top.”
(Editing by Toby Davis and Ken Ferris)