Dustin Pedroia follows through on a single during the fifth inning. He added a grand slam in the eighth.

AP / Frank Franklin II

NEW YORK — The newcomers are coming through for the Red Sox.

Jason Bay has become a statistical machine for Boston. Paul Byrd has brought stability to the rotation. Now Mark Kotsay will attempt to become a contributor.

“It’s been great,” said Byrd. “ Mike Lowell, the World Series MVP, goes down. J.D. is hurting a little bit and the pitching staff is hurt a little bit. I come over and help out, and now we’ve got Kotsay. This is just a great group of guys with great chemistry in this clubhouse. I’ve been here two weeks and I already feel like I fit in. It’s a credit to these guys already here and the guys they brought it.”

The only thing that went wrong for the Red Sox in their 11-3 pounding of the Yankees was when Byrd was hit on the head by a foul ball even before he threw his first pitch last night at Yankee Stadium.

Boston’s newest addition to the rotation was sitting in the visitors’ dugout when Kevin Youkilis turned on a pitch and lined it into the bench area. The ball ricocheted around before hitting Byrd in the back of the head. The veteran right-hander was holding the back of his skull and was briefly checked out by team trainer Paul Lessard.

But that was the only bad thing that happened to the Red Sox.

“I got hit in the back of the head, and it’s the first time I’ve been thinking clearly all week,” Byrd said. “It hurt. It smoked me right in the back of the head. I was walking around and somebody came over and said, ‘All that did was make you mad, right? You’re ready to go.’ I just smiled.”

The fact is the Red Sox have been a major headache for the Yankees the last couple of days in the Bronx, and they are now one victory from a three-game sweep.

While Byrd earned his second victory (three starts) after working six solid innings, allowing two runs on five hits with two walks and five strikeouts, new Red Sox outfielder Bay has wreaked havoc on the Yankees.

Bay went 2-for-4 with four RBI, and now has recorded two or more hits for the 10th time in his 23 games for the Red Sox. He’s also hitting .347, with 22 runs, 4 doubles, 2 triples, 4 homers and 24 RBI since he came to Boston in a three-team deal that involved Manny Ramirez.

“Jason’s been great,” said Byrd. “He’s a quiet superstar. You don’t have to hear about him all the time and he’s not looking for tons of attention. He just goes out and gets the job done and he plays hard.”

Even though the newcomers have been key for Boston, mainstay Dustin Pedroia has been huge. He went 3-for-5 and recorded his first career grand slam in the seven-run eighth inning for Boston.

“I don’t think any of us are capable of knowing how many he can hit,” said Red Sox manager Terry Francona. “He swings hard and he squares up the ball.”

The Red Sox knew coming into this three-game set that they had an opportunity to pound the Yankees nearly into submission by winning this series, and a sweep today could really finish the job.

Last night Boston continued its recent offensive attack and quickly got to Yankees starter Sidney Ponson by scoring two runs in the top of the first inning. With two outs and two on, Bay hit a two-run double for the early advantage.

New York superstar Alex Rodriguez, who was criticized on Tuesday for his horrendous 0-for-5 performance, responded last night during his first at-bat against Byrd by hitting an RBI double. A-Rod added his second hit in the fourth inning, a double to left-center, and later scored on Robinson Cano’s single that tied the game at 2-2.

Boston continued its attack on Ponson in the fifth, scoring twice on a bit of fundamental baseball.

With one out, Jacoby Ellsbury reached on a single to right field before a perfectly executed hit-and-run with Pedroia put runners on the corners. David Ortiz drew a walk to load the bases and Kevin Youkilis followed with another walk to push the Sox’ third run across. Bay followed with a sacrifice fly as Boston gained a 4-2 lead.

Prior to last night’s game, Francona spoke about the head-scratching, mind-numbing inconsistency of reliever Manny Delcarmen. The hard-throwing right-hander struggled on Tuesday night and needed his fellow relievers to bail him out, which they did.

Fast forward to last night.

With the Sox holding a two-run lead and Byrd finished for the night, Delcarmen entered the game in the bottom of the seventh inning and retired the side in order, including two strikeouts.

That proved crucial for the Red Sox and Delcarmen because Bay continued his offensive show with an RBI triple in the top of the eighth. The Sox then loaded the bases, and Alex Cora hit a sacrifice fly and Coco Crisp contributed an RBI single for a 7-2 lead against the lifeless Yankees.

Boston wasn’t even close to being done.

Ellsbury loaded the bases again when he singled to right before Pedroia launched his first career grand slam, giving the Red Sox an 11-2 lead. New York added one more run, on a solo home run by Jason Giambi, in the ninth.

jmcdonal@projo.com