LOUISVILLE, Ky. — Phil Mickelson won as many points as his last two Ryder Cups combined. Justin Leonard had never won a match in any Ryder Cup until two blowout victories at Valhalla.

And the most stunning turnaround Friday might have been all those celebrations.

Finally, the Americans had all the fun.

Boo Weekley revved up the crowd, Anthony Kim set a record for high-fives and the Americans delivered four big comebacks to take a 51/2-2 1/2 lead, their largest margin after the opening day since Europe first was included in the Ryder Cup in 1979.

"We're in a good place," U.S. captain Paul Azinger said. "Who would have thought?"

The Americans had not led after any session since last winning the Ryder Cup in the "Miracle at Brookline" in 1999. But with six rookies and no Tiger Woods, they lost only one of eight matches and left European captain Nick Faldo wringing his hands.

Europe has won the Ryder Cup the last three times, and five of the last six, but now finds itself desperate to catch up.

"We've had a tough time," Faldo said. "We lost a few points, but we haven't lost any spirit."

One of the few bright spots for Europe was Lee Westwood, who tied Arnold Palmer by running his unbeaten streak in the Ryder Cup to 12 matches. Westwood and Soren Hansen birdied the last three holes in the final fourballs match of the afternoon, the final birdie enough to earn a halve against Weekley and big-hitting J.B. Holmes.

Even so, it was an amazing start for the Americans.

In the opening match, Mickelson and Kim trailed by three holes with six to play until winning three straight holes and earning a halve against double major winner Padraig Harrington and Robert Karlsson. Down by three after four holes in the afternoon, Kim gave them their first lead of the day with a 7-foot birdie on the 14th, and Mickelson dropped in a 20-foot birdie on the 17th that led to a 2-up victory.

"We played with a lot of heart and a lot of emotion today to pull the halve and win out," Mickelson said. "We have a lot of work to do. This is a fun day. I love playing with this guy. Anthony has got this youthfulness to him, and he has a lot of game."

It was a big day for most of the U.S. rookies, who went 3-2-2.

Leonard teamed with one of those rookies, Hunter Mahan, and they won both matches without reaching the 17th hole. The afternoon victory came at the expense of Sergio Garcia, who finally looked ordinary in the Ryder Cup.