Phil Mickelson was reluctant to take on a leadership role for the United States at this week's Ryder Cup, despite being the most experienced American on the 12-man team.

The left-hander will be representing his country for the seventh time in the biennial competition but believes U.S. captain Paul Azinger has given the hosts requisite direction and guidance.

"My only responsibility is to play well," world number two Mickelson told reporters on Tuesday after the first official day of practice at Valhalla Golf Club.

"That's something I've been working on and all of the players have been working hard on. We are all getting ready and hopefully we'll be sharp and have our 'A' game because we know that our competition is very strong.

"I think captain Azinger has been a wonderful leader for us," added Mickelson of a U.S. team containing six rookies.

"One of the biggest challenges heading into a Ryder Cup is some of the uncertainty we'll face during the week. He's been a great captain and has given us great direction."

Mickelson has tasted victory only once in six matches against Europe and concedes the Americans will go into this week's matches as clear underdogs.

"I don't feel there's a question about that. Given our play and given the fact that we've lost our top player, that's the case," he said, referring to the absence of injured world number one Tiger Woods.

"But it doesn't mean that we can't come out and play well and, with the help of the crowd and with a golf course that's very well suited for many of our players, have a great week and possibly come out on top."

Europe are bidding for a fourth successive victory over the Americans. They won the last two matches by record-equalling margins of 18-1/2 points to 9-1/2.