CINCINNATI — Two challenges lost too early, a memorable rookie debut, an umpire gone awry, a manager ejected, a shortstop irate. The second game of the season for the Boston Red Sox seemingly had it all, except for a victory.

The Red Sox fell 6-5 to the Cincinnati Reds on a walkoff single in the 11th inning, and that was just the culmination of a frustrating day on the field.

Throughout the game, the Red Sox and Reds took issue with home-plate umpire CB Bucknor’s strike zone. The longtime umpire had eight calls challenged under the new Automated Ball-Strike Challenge System with six of them overturned. There likely would have been at least two more if the Red Sox hadn’t lost their two challenges by the third inning.

“He has one job to do, it’s call balls and strikes,” manager Alex Cora, who was ejected by Bucknor in the eighth inning, said. “It wasn’t his best day. That’s what the system does. It’s out there. Everybody sees it, and he’ll be the first one to accept it. I saw him putting his head down after one of the challenges. We’re all human. It’s not easy, what we do and what he does.”

The Red Sox battled from behind all day, put themselves in an early hole after a rocky start from Sonny Gray but made the day harder on themselves by losing their two challenges early. Catcher Carlos Narváez lost one by trying to get a strike for Gray in the second inning, and then leadoff hitter Roman Anthony challenged a strike call in the third that proved to be a ball. That left the Red Sox without the ability to challenge Bucknor’s calls through the ninth inning.

“It just goes back to me kind of wasting that second one,” Anthony said. “It can’t happen. And unfortunately, you just lose them. We saw how that worked out. It’s a lesson. We’ll take it as a lesson, at least I will.”

But even without the challenges, the Red Sox missed opportunities throughout the afternoon, leaving 11 men on base and going 2-for-14 with runners in scoring position, an issue that plagued their offense last season.

Trevor Story high-fives teammates after hitting a home run.

Trevor Story’s third-inning home run cut the Reds’ lead to 3-1. (Aaron Doster / Imagn Images)

Still, they managed to stay within striking distance, making Bucknor’s shoddy strike zone all the more aggravating.

In the eighth, it all came to a head. With two on and two out and the Red Sox trailing 5-4, shortstop Trevor Story came to the plate. On an 0-2 pitch, he appeared to check his swing but was rung up by Bucknor, who did not check with first-base umpire Adam Beck for the appeal. Bucknor had likely missed another pitch earlier in a Story at-bat, but the shortstop couldn’t challenge.

Normally mild-mannered, Story didn’t hold back his emotions, growing increasingly angry as he shouted at Bucknor and had to be held back by Cora and third-base coach José David Flores, who’d run over to prevent Story from getting ejected.

“Just obviously disagree with the call real strongly,” Story said after the game. “I think a lot of people did too. I told him my piece, what we said was what we said out there. And I don’t have anything really good to say about the situation, so I’m not going to say anything else.”

After Cora had pushed Story back to the dugout, he had his own words for Bucknor, who promptly ejected him.

“We learned a lot today,” Cora said. “From my end, there were some calls that we didn’t agree (with), but we had no challenges. So we had to live with it.”

As players get used to the ABS system, ensuring they don’t waste challenges too early in the game will be something Cora continues to preach.

“We will talk to the players and that’s it,” Cora said. “One was by half an inch, but still, we just gotta know the situation. We’ve been talking about it the whole spring. Two days ago, we were very excited about ABS. And today, we’re not too happy with it. The system is the system. We’re not happy with the way things went up today. But that’s on us.”

In the sixth inning, Bucknor missed back-to-back calls with reliever Ryan Watson, making his big-league debut, on the mound.

Watson entered with two on and two outs with the Red Sox trailing 5-3 and walked the first batter to load the bases with Eugenio Suárez up. On a 1-2 pitch, Bucknor rang up Suárez as Watson pumped his fist and began to walk off the mound, but Suárez immediately tapped his helmet to challenge. The review on the video board showed a ball. Watson returned to the mound and again fired a pitch in the pressure-packed situation. Again, Bucknor rang up Suárez, and once again the hitter challenged. The video review, again, showed a ball as the crowd roared with delight.

“That’s probably the loudest I’ve heard a stadium while pitching,” Watson said. “So it was intense, for sure.”

Watson found his composure and induced a hard grounder on the next pitch that Marcelo Mayer snagged, ranging behind the second-base bag and making a nice throw to first for the out.

“It was a very up-and-down emotional at-bat against Suárez there,” Watson said. “But I felt like I was able to lock back in after the two overturned calls there and get a groundball.”

Despite the missed opportunities to drive in more runs, the Red Sox pulled within 5-4 in the seventh on a Wilyer Abreu double before Abreu tied the score with a monstrous solo homer in the top of the ninth.

But they didn’t have enough for a come-from-behind victory as Dane Myers’ RBI single in the 11th off Justin Slaten sealed the win for the Reds.

The challenge system will be a work in progress, but Saturday proved a hard lesson for the Red Sox.

“I think it’s a learning moment for sure,” Story said. “We have a lot of trust in all of our guys, so we don’t want to be up there hesitant at all, but it’s a good learning moment and it’s early in the season and we can kind of make the adjustments.”