Rookie shortstop Jed Lowrie, center, is swarmed by teammates after his 12th-nning single drove in Jason Bay (not shown) to give the Sox a 2-1 victory.

The Providence Journal / Gretchen Ertl

BOSTON — The Red Sox still had a cleanup hitter and a left fielder in their lineup last night. No one was missing. Manager Terry Francona still penciled in nine names onto the lineup card. And fans in the Monster Seats still had someone to cheer for.

But that player was someone other than Manny Ramirez.

Red Sox newcomer Jason Bay, wearing No. 44, manned the left-field grass and hit fifth in the order — Mike Lowell served as Boston’s cleanup hitter — as Bay made his debut at Fenway Park as a member of the hometown nine.

And the fans gave him a friendly Fenway welcome.

During pregame introductions, Bay was stretching and running sprints in right field with a few of his new teammates when he name was announced. The crowd stood and cheered until he tipped his cap in appreciation.

When he made his first appearance in the bottom of the second inning, it was much of the same.

The 37,832 in attendance gave him a standing ovation and he acknowledged it with a tip of his helmet and a brief wave. The cheering was so loud he had to step out of the batter’s box to regain his composure, before drawing a five-pitch walk, which again, drew an ovation.

“The ovation was a little unexpected,” he said. “At the plate, I wasn’t sure what to do with that. It was very flattering. I hadn’t even played an inning yet and to get that ovation was nice. It was a nice welcome.”

He reached third on a J.D. Drew double before scoring on Jed Lowrie’s sacrifice fly to left field to give Boston a 1-0 lead. When Bay crossed home plate, he received another ovation and was given a hero’s welcome from his new teammates when he got to the dugout.

Not only did he score a run, he proved he can play defense and handle the left-field wall. With the Sox holding a 1-0 lead in the top of the fifth inning, Oakland had a runner on third when Ryan Sweeney lifted a high fly ball to shallow left field. Bay, in an all-out sprint, made a tremendous sliding catch to secure the lead.

After the A’s knotted the game at 1-1 and had the potential go-ahead run in scoring position in the ninth, Bay made a routine play on the run to end the inning.

He finished his first game with the Sox 1-for-3 with two runs scored and a triple, which resulted in the game-winning run in the bottom of the 12th inning. In addition, he struck out twice, walked twice and was a hit by pitch.

It was an interesting 24 hours for Bay and the Red Sox.

“It’s pretty exciting,” said Bay. “It has been kind of a whirlwind. When the trade deadline was done at 4 o’clock, I didn’t hear anything. I didn’t hear anything until about a half-hour after that. We were getting on a bus to go to Chicago [when he was told of the deal]. My head was spinning.”

Red Sox general manager Theo Epstein felt satisfied everything worked out for everyone involved.

“We feel good about the trade,” he said. “There were a lot of difficult circumstances and we made something good come out of it. We got a really good player who will help out the club and is under our control [signed contract] for next year.

Given the totality of the circumstances it was the right thing to do. We didn’t make the trade because of what happened last week. It was a longer story than that.”

Bay is at the opposite end of the spectrum when compared to Ramirez. He won’t be high-fiving fans. He won’t be going to the bathroom in the Monster. He may not put up the Hall of Fame numbers Ramirez did here, but he’s not expected to.

“I’m not going to be Manny Ramirez,” Bay said. “I’m equipped to handle [those expectations] and I understand they’ll be out there. I’m not going to try to replace anybody. They just needed another left fielder. I’ll play left field. I can’t wait.”

Sean Casey spent only five months in Pittsburgh (2006) and was a teammate of Bay during that time. The two talked after the deal on Thursday, and Casey told him to just be himself.

“He’s going to be a great fit here,” said Casey. “You’re going to love Jason Bay. He’s a great player, and as good as a player, he’s a great person, too. He’s a great teammate. He goes about his business hard everyday and you’ll never see him dog anything, ever. These people just want somebody to go out there and play hard, and play the game the way its supposed to be play. J-Bay is going to do that; there’s no doubt about it.”

Red Sox third baseman Kevin Youkilis, who had a run-in with Ramirez in the dugout on June 5 at Fenway Park, said Bay will be a welcome addition to the club moving forward.

“We’re happy Jason Bay is here because he’s a great guy,” said Youkilis. “I’ve talked to a couple of his teammates in Pittsburgh and they’ve said he’s a really good teammate. If you’re going to replace Manny Ramirez — you’re not going to replace his stats — but if you’re going to replace him, you hope you get a good teammate and that’s what we got.”

Even before he was told he would be playing for the Red Sox, Bay knew the history and legacy of this franchise, learning everything Red Sox from his father, Dave, who has always been a diehard Red Sox fan, according to Bay.

With all the standing ovations. With all the notoriety, surrounding his arrival, the 29-year-old Canadian native seems to be fitting in here.

“I had a lot of people asking to help me with my bags at the airport,” he joked. “It was a little overwhelming. Everybody says the fans here are the best and I can’t help looking forward to it.”

jmcdonal@projo.com