WASHINGTON - The Phillies' top pitching addition during the off-season received most of the attention and much more of the money than the team's addition in the field.

It wasn't until Monday afternoon at Nationals Park that Placido Polanco finally shared top billing with Roy Halladay. While Halladay delivered a dominating seven-inning performance in his Phillies debut, Polanco accounted for a career-high six RBIs during an 11-1 season-opening rout of Washington.

Four of those six RBIs came on one seventh-inning swing when Polanco sent a 1-0 pitch into the Phillies' bullpen in left field for his second career grand slam.

"I knew I hit it pretty good," Polanco said. "I was just trying to get a sacrifice fly or something. Having Chase [Utley] hitting behind me, I think I'm going to be seeing a lot of fastballs, so I have to be ready. I wanted a pitch I could drive and I got it. It was good timing - my first day back with the Phillies."

After spending four-plus seasons with the Detroit Tigers following a June 2005 trade from the Phillies, Polanco said he doesn't feel like a newcomer in the clubhouse. His teammates don't consider him one, either.

"He's a returning player," shortstop Jimmy Rollins said.

Rollins might not consider Polanco a new addition, but Rollins does rank his presence in the lineup right up there with Halladay's role at the top of the Phillies' rotation.

"Getting Roy Halladay is one of the biggest moves we've made since I've been here," Rollins said. "Then you balance the lineup with a guy like Polanco - not just a righthanded bat, but a guy who can actually move the ball around and be big for us in situational at-bats. That's what gives us more balance, and it doesn't leave all the pressure up to Chase and Ryan [Howard] all the time."

Polanco, who signed a three-year, $17 million deal to rejoin the Phillies, accounted for his first RBI with a sacrifice fly that completed a five-run rally in the fourth inning. Two innings later, he singled home Rollins after the shortstop had tripled.

Howard said he wasn't the least bit surprised by Polanco's big opening-day performance.

"I've been watching Polly hit all spring, and he just puts together great at-bats," Howard said. "He's just a hitting machine. He goes up and gives you good at-bats, and he's going to put the ball in play. When you put the ball in play, good things happen."

Polanco did give a preview of things to come in spring training by hitting .371 with a .409 on-base average, but he's also been one of the best contact hitters for a long time.

"I think coming into this, we all knew he was the right man for the job," rightfielder Jayson Werth said. "It just opens up so many other avenues for our offense. You have a guy like Shane [Victorino] hitting [seventh], that's a potent lineup. We look to build on it. Today Polly had a big day, and Wednesday we'll come back, and who knows who it will be."

That's what Polanco loves about his old team that is now his new team again.

"When I left here, these guys were coming up," Polanco said. "Chase, Howard, and all those guys. You could see the talent. You could see it was just a matter of time before they put everything together, and they did it very quick. And the team only gets better. They still have young guys that are hungry with a lot of talent."

And now they also have Polanco to make things even better.

Contact staff writer Bob Brookover at 215-854-2577 or bbrookover@phillynews.com.