Andy Roddick made a winning start to his Australian Open campaign but was unhappy with a line judge after a collision with the courtside official.
Wimbledon runner-up Roddick posted a 6-1 6-4 6-4 win over Dutchman Thiemo de Bakker, maintaining the form which saw him win the Brisbane International.
But American Roddick, who has returned to action this month following a knee injury, was scathing with his criticism of the line judge whose foot he tripped over early in the match as he raced to make a return.
He told the official to "move out of the way when you see a player coming" and later expanded on his thoughts, saying: "I ran into one of those immovable objects called a referee (line judge).
"He wasn't giving up any ground. I didn't see him. He wasn't really trying to do much to get out of the way.
"Normally they see a player running full speed, they decide to at least move or catch the player."
Fortunately Roddick did not suffer a recurrence of his injury, admitting he had merely "pinched" the knee.
"I promise you that first step afterwards was a relief," he said.
"It kind of jarred a little bit. But it's a good sign that I can take that."
Regarding his performance, Roddick said: "I could have executed probably a little bit better at times. But overall I thought it was pretty good."
Roddick, the seventh seed, was joined in the second round by Britain's Andy Murray, as the fifth seed romped to a 6-1 6-1 6-2 win against South African Kevin Anderson.
Eleventh seed Fernando Gonzalez did not have such a smooth run, but the Chilean was ultimately too strong for Belgium's Olivier Rochus and prevailed 6-3 6-4 3-6 6-1.
Czech player Radek Stepanek, seeded 13th, became the first major casualty in the men's event but his defeat to big-serving Croatian Ivo Karlovic was not a huge upset.
Karlovic finished 2009 in disappointing form but was a top-16 player less than 18 months ago and has a serve which can win him matches.
Karlovic dropped the first set but fought back to win 2-6 7-6 (7/5) 6-4 3-6 6-4.
Croatia's Ivan Ljubicic trounced Australian Jason Kubler, the 24th seed beating the home hope 6-1 6-2 6-2, and an all-German first-round tie provided the comeback story of the day.
Philipp Petzschner appeared in complete control of his match against Florian Meyer when he won the first two sets for the loss of just two games.
However, the tussle turned around and Meyer won it 0-6 2-6 6-4 6-2 6-2.