BALTIMORE–An hour before game time, fans were allowed in the ballpark. They were eager for their first live look at Baltimore Orioles baseball since September 22, 2019.

With just 10,150 fans allowed inside Oriole Park at Camden Yards, it wasn’t a normal Opening Day. Instead of running in from behind the center field wall, the orange carpet was relocated, and players trotted from the dugout to the first base line.

Everyone wanted to see Trey Mancini and wish him well a year after he had colon cancer surgery. He was greeted warmly when he was introduced, and then again when he batted in the first.

“It was nothing short of what I expected,” Mancini said. “We’ve got the best fans in baseball here. No matter what, they love us. That showed today. That meant the world to me. Even though it was 25 percent capacity, it felt like it was a full stadium out there.”

The Boston Red Sox joined in the applause when Mancini was introduced. When he came to bat, he doffed his helmet to acknowledge the crowd.

“When I came out on the mini orange carpet, I wasn’t expecting a prolonged ovation then. When I was hitting, I fought back some tears there when I got the first ovation. That’s probably what will stay with me the most.”

Mancini was 1-for-4 as the Orioles lost their home opener to the Boston Red Sox, 7-3, on Thursday. They’re 4-3.

Manager Brandon Hyde exploded when Rio Ruiz, who was hit by a pitch by Boston’s Eduardo Rodriguez, was ruled to have swung by third base umpire Scott Barry. Hyde was immediately ejected.

“I thought Rio checked his swing,” Hyde said. “The ball hit him, and then his body because of the hit by pitch took him over the plate like a swing.”

Hyde checked to make sure Ruiz was OK.. While out there, he loudly asked home plate umpire Jeremie Rehak and Barry about the call.

“I asked one too many times, I guess,” Hyde said. “That’s the quickest ejection I’ve ever had. I was very surprised by it.”

Mancini said that he hadn’t seen Hyde that upset.

“That was awesome, though,” Mancini said. “He came out there fiery. We love Hyder. Whenever you have a manager back you up like that in that situation, it means a lot to the guys. It always fires you up when something like that happens.”

Ryan Mountcastle hit a home run to center but had another tough game in left. On Wednesday night, he misplayed Gary Sanchez’s fly ball at Yankee Stadium that allowed the Yankees to tie the score. In the sixth inning Thursday, with the Orioles holding a 3-2 lead, Mountcastle chased Christian Vazquez’s pop to left, and then as he neared it, he stopped running.

After Boston had taken a 4-3 lead, Franchy Cordero singled to left, and Mountcastle’s errant relay allowed Cordero to get an extra base.

“I think he’s putting a lot of pressure on himself in the outfield,” Hyde said. “A couple of plays he wished he would have made. The last couple nights have been rough for him defensively … It just hasn’t happened for him the last couple of nights.”

Orioles starter Matt Harvey allowed four runs on seven hits in five-plus innings for the loss. He was glad to be part of Mancini’s homecoming.

“His first at-bat was pretty amazing as well and sitting in the dugout to experience that was special,” Harvey said. “I’m honored to be his teammate.”

Relief pitchers Dillon Tate, Shawn Armstrong and Rule 5 pick Tyler Wells each gave up a run.

“Tough assignment today, a day game after a night game on the road,” Hyde said. “Get in in the middle of the night, and I’m asking these guys to get outs against a really good lineup.”

On Wednesday, the Orioles won despite getting only four hits in 11 innings. Against the Red Sox, they stopped hitting after Severino’s home run, their fourth hit.

Eleven straight Orioles were retired until Pat Valaika walked, leading off the eighth. Two batters later, Mancini singled for the Orioles’ fifth and final hit.

Boston starter Eduardo Rodriguez, who also missed the 2020 season, allowed three runs on four hits in five innings. Rodriguez was out because of myocarditis, an inflammation of the heart muscle.

Boston Rule 5 pick Garrett Whitlock pitched two perfect innings. Matt Andriese worked the eighth, and Matt Barnes struck out Maikel Franco, Pedro Severino and Freddy Galvis in the ninth.

The Orioles struck out 14 times. They’ve struck out 13 or more times in the last five games, a major league record.

Hyde noticed the impact the fans had on the game.

“It definitely raises the intensity of the game,” Hyde said. “There’s definitely more emotion in the game with fans, home and away. Our fans were great today. The players fed off the emotion early.

”It’s unfortunate that we couldn’t hold on. It’s unfortunate that we couldn’t get some rallies going, really from the fifth inning on. I thought it was great for our players to play in front of our home fans, and it’s a good feeling to hear the fans back at Camden Yards.”

Notes: Centerfielder Cedric Mullins has hit in each of the Orioles’ seven games. … Hyde’s ejection was his fifth as Orioles manager.