By Alex Perry BBC Sport at Wimbledon

The US Open is the big one for me now Lleyton Hewitt Match report: Hewitt v Karlovic

All the talk on the first morning at Wimbledon was of a proposed boycott by the ATP of next year's tournament.

Lleyton Hewitt will probably now be wishing they had got their act together in time for this year's event after becoming the first men's reigning champion to lose in the first round since the Open era began.

Hewitt was remarkably calm afterwards, and refused to make any excuses for his defeat at the hands of the little known Croat Ivo Karlovic.

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The only time Hewitt showed any signs of his famous temper was when he was asked whether his recent split from coach Jason Stoltenberg, or pending lawsuit against the ATP had disrupted his game.

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"No, not at all," said Hewitt emphatically.

"I felt like I was hitting the ball pretty well," he insisted. "I just didn't take my chances."

Nevertheless, many will still question his decision to go it alone.

HAVE YOUR SAY Something is wrong with Hewitt, and it's got nothing to do with tennis From Kevin, Dublin Join the debate

The Australian points to tournament wins in Scottsdale and Indian Wells earlier in the year, and suggests it is only his Grand Slam performances that have let him down.

And two of those were while he was still with Stoltenberg.

"My Grand Slams have been pretty disappointing in terms of results.

"But I don't think I did too much wrong against El Aynaoui [in Australia], and the first two sets against Robredo [at Roland Garros] were probably the best I've ever played on clay.

"This has been the most disappointing of all the Slams."

FACTS: HEWITT V KARLOVIC Age: Hewitt: 22 Karlovic: 24 Titles: Hewitt: 19 Karlovic: 0 Grand Slam win-loss: Hewitt: 52-19 Karlovic: 1-0 Career earnings (to 2003) Hewitt: $10,862,801 Karlovic: $37,387 Highest world ranking: Hewitt: 1 Karlovic: 175 Other SW19 shockers Karlovic: the quiet assassin

But Hewitt preferred to give credit to his opponent for this defeat than blame himself.

"There wasn't too much I could do on the breakpoints," he said.

"I had one early in the third set and another at the start of the fourth set, and he hit two aces.

"When I missed those opportunities early in the second set, his whole game came together.

"Early on I felt pretty good - it just shows how quickly things can change."

Hewitt has one more Slam this year to try to put things right.

"I hope I can learn from this," he said. "The US Open is somewhere I've had good results - that's the big one for me now."