BOSTON -- The Boston Celtics brought new meaning to the term "reigning" world champions on Friday at Fenway Park.

Just as the Red Sox were beginning an on-the-field ceremony dedicated to the new NBA champs prior to a tilt with the St. Louis Cardinals, rain doused the packed ballpark and grounds crew members raced to put the tarp over of the infield dirt. The game was put on an official rain delay minutes after the conclusion of the ceremony.

Fortunately for the Celtics, the celebration included all involved being patrolled around the warning track on three Boston Duck Tour boats. Still, it was a celebration much appreciated by the Boston faithful, who waited 22 years between the team's 16th and 17th championship banners.

"We're really proud of what they did, and we're happy for them," said Red Sox vice president/general manager Theo Epstein. "We thought we'd take the occasion tonight to celebrate a little bit."

A shamrock christened the center-field grass and the players donned green jerseys to commemorate the occasion. The Red Sox were on a road trip when the Celtics downed the Los Angeles Lakers, 131-92, in Game 6 on Tuesday night.

A city known for its sports teams' struggles and shortcomings through much of the 20th century -- highlighted by the Sox's 86-year World Series drought -- Friday's celebration marked the sixth championship combined between the Red Sox, Celtics and New England Patriots since 2001.

"It's pretty cool, man," Jonathan Papelbon said. "You know, city of champions. I think now they've got a team they've put together -- a championship team, obviously -- that's status quo in Boston."

The tribute in the Red Sox's front office clearly began well before the Celtics took the field for pregame festivities. Epstein wore a Celtics hat to the team's press conference earlier in the afternoon.

Sox manager Terry Francona, who is friends with Celtics coach Doc Rivers, said the team's success is well deserved for an organization filled with classy individuals.

"They've got some great people all the way through their organization," Francona said before the ceremony. "Like Theo kind of said, it'll be fun to see them kind of take their bows, because we're happy for them."

And Francona said he is by no means a bandwagon fan, having enjoyed the Celtics' team long before it took home the title on Tuesday.

"I liked the Celtics when they were winning 26 games," Francona said. "Now that they've done what they've done, it's been really fun to watch."

To kick off the game, Celtics captain Paul Pierce threw out the ceremonial first pitch.