PITTSBURGH— The Pittsburgh Pirates' last line of defense is also their best source of offense.

At least, it was.

Through 102 games this season, Jason Bay, Nate McLouth and Xavier Nady continued to comprise the major baseball's most productive outfield.

Left fielder Bay is hitting .290 with 22 homers and 61 RBI. Center fielder McLouth is hitting .280 with 21 homers and 70 RBI. Right fielder Nady is hitting .330 with 13 homers and 57 RBI.

But Nady and left-handed relief ace Damaso Marte were traded to the New York Yankees Friday night for four prospects, three of them pitchers.

"I've played alongside some pretty good center fielders and left fielders in my career, but I was never part of an outfield clicking like this," Nady said.

McLouth concurred.

"Not even in the minor leagues," the first-year starting center fielder said. "Guys go on streaks, but this has lasted for a while.

"We've been getting a lot of clutch hits and guys keep getting on base in front of us."

Numbers don't lie in that regard. McLouth is hitting .324 with runners in scoring position — .357 in those situations with two outs — while Nady is hitting .322 with runners in scoring position.

The Pirates have won 14 of 16 games in which Bay collects two RBI, 26 of 40 games in which Bay knocks in at least one.

Bay and McLouth are having a playful battle for the team home run lead. Four innings after Bay hit his 22nd home run Thursday night, McLouth belted his 21st.

"I knew that was coming,"Bay said, laughing. "It wasn't going to take him long. There's a good rapport between all three of us. We keep each other going."

Bay is tied for eighth in the National League in home runs, Nady is fifth in batting average and McLouth leads the circuit with 34 doubles.

So much attention has been paid to the offensive production of the Pirates' outfield that its defensive ability has been overlooked.

McLouth is the only NLcenter fielder without a fielding error in 2008 — the Angels' Torii Hunter is the only American League center fielder who can make that claim — and Nady led the senior circuit with 10 assists before joining the American League.

"We take pride in our defense,"McLouth said. "Saving a run carries the same effect as driving in a run."

After collecting only one hit while his team fell victim to a four-game sweep in Colorado, Bay was 8-for-17 with three homers and seven RBIin four games entering Friday night's 6-5 loss to San Diego.

"Maybe it took me a few games to get back in the groove, I don't know,"Bay said. "I'm feeling pretty comfortable at the plate right now."

Bay is one of just four players in the 122-year history of the Pirates franchise to hit at least 20 home runs in five straight seasons. Willie Stargell, Frank Thomas and Ralph Kiner are the others.

Nady rode a 13-game hitting streak into Friday night — tied with Cincinnati's Jay Bruce for the longest active streak in the big leagues — after compiling a career-best 14-game streak back in April.

"This is the first year in a long time that I've been healthy and it's making a difference," he said. "Even with that, I missed 10 or 12 games earlier with an injury."

Nady jammed a shoulder running into a wall in Baltimore while trying to catch a foul ball.

"It's tough missing (at-bats), especially when you're hitting well,"Nady said. "But when you play the game hard, you never know when something like that's going to happen.

"Jason had a knee problem last year and he's recovered. I've stayed relatively healthy and Nate won the center field job in spring training.

"Maybe we're an unlikely combination, but, hey, it's working,"Nady added.

At least, it was.