Argentina's Juan Martin del Potro had to work harder than expected at the start of his U.S. Open campaign, struggling to put away Spanish journeyman Guillermo Garcia Lopez 6-3, 6-7 (5-7), 6-4, 7-6 (9-7) in first-round action.

Del Potro, the 2009 champion, seemed headed to a routine victory Wednesday after winning the first set with two breaks of serve.

But the No. 6 seed struggled to take advantage of his break-point opportunities the rest of the way, converting only 2 of 11 chances over the final three sets against his 74th-ranked opponent.

"It was a typical first match of a tournament like the Open, where I was up against a good player who hit effectively from the back of the court and made me work," Del Potro said after his grueling victory in four hours and 13 minutes.

Each of the last three sets took at least one hour and 10 minutes to play.

Next up for the big Argentine in the second round will be 32-year-old Lleyton Hewitt, the 2001 champion, who defeated American Brian Baker 6-3, 4-6, 6-3, 6-4.

In Wednesday's night match, defending champion Andy Murray of Scotland coasted to a 6-2, 6-4, 6-3 win over Frenchman Michael Llodra.

Murray went down a break of serve early in the second set but he recovered quickly and clinched the match in just one hour and 38 minutes.

In the most emotional match of Wednesday's session, 33-year-old American James Blake's career came to an end with his 6-7 (2-7), 3-6, 6-4, 7-6 (7-2), 7-6 (7-2) first-round loss to big-serving Croatian Ivo Karlovic, who threw down 38 aces.

Blake, a former world No. 4 who reached the U.S. Open quarterfinals in 2005 and 2006, had announced that he would retire from tennis after competing in this year's event. EFE