SAN FRANCISCO -- The Joey Bart era has arrived.

The Giants promoted Bart, who is ranked the club’s No. 1 prospect and No. 15 on MLB Pipeline’s Top 100 Prospects list, to their 28-man roster ahead of Thursday’s series finale against the Angels at Oracle Park.

San Francisco optioned fellow backstop Tyler Heineman to the alternate training site in Sacramento and designated outfielder Joe McCarthy for assignment to clear spots on the 28- and 40-man rosters, respectively.

Bart, 23, was slotted into the lineup at catcher, batting sixth against Los Angeles left-hander José Suarez in his Major League debut.

“It was unbelievable,” Bart said. “I was shaking for it seemed like 30 minutes and I couldn’t stop shaking. I’m just really, really blessed to be here and be healthy and to move forward with the team.” 

Bart, the second overall pick of the 2018 MLB Draft, is viewed as the heir apparent to star catcher Buster Posey, who elected not to play this season after adopting twin girls. With Posey out, the Giants will receive their first big league glimpse of Bart, who is expected to be a foundational piece for the club’s developing core of young position players.

“I think I'm just excited to see a guy that looked great in the batter's box in our secondary camp do it on the big stage,” manager Gabe Kapler said. “I'm excited to see all the work that I know he's done through the reports that I've gotten from [farm director] Kyle [Haines] and others from Sacramento. I know we're all fired up about seeing him in the lineup.”

Bart wasn’t viewed as a candidate for the Opening Day roster, as president of baseball operations Farhan Zaidi and Kapler repeatedly said they believed he needed more development before he was ready to ascend to the Majors. But Bart emerged as the most impressive catcher over the club’s three-week Summer Camp at Oracle Park, consistently flashing his opposite-field power and his elite throwing arm behind the plate.

“Bart is unbelievable,” right-hander Dereck Rodríguez said. “He’s a big league player. He’s awesome to throw to. He’s awesome calling games. He looks like a veteran at the plate.”

Bart opened the season at the Giants’ alternate training site, where he logged regular catching reps to help make up for the time he missed last year after suffering two separate hand fractures.

“We wanted to bring him up when we had conviction he was ready to take the job and run with it and not be in a situation where every game and every at-bat was going to be a referendum on his readiness,” Zaidi said. “We just feel like with his progress, he’s at that point now.”

Zaidi said he spoke with Bart on Wednesday afternoon to check in on his progress, but he didn’t tell him that the Giants were planning on calling him up until a second conference call later that night with general manager Scott Harris and Kapler.

“Those conversations never get old,” Zaidi said. “They're the best part of the job. Just to add a little twist of cruelty, I pretended that it was just a follow-up to the conversation we've had earlier in the day. He was probably thinking, ‘I gotta have another 20-minute conversation with this guy?’

“But when he called me, we were all on the phone and gave him the news. It's overwhelming. He's super excited. It felt even better delivering the news knowing how hard he's worked in Sacramento in that environment. He's had to quiet up the noise as well. I think he's done an amazing job.”

Zaidi said he expects Bart to take over as the Giants’ No. 1 catcher now that he’s reached the Majors. While he received exposure at first base in Sacramento, the Giants don’t expect him to see much time there until 2021, when they’ll have to figure out a way to get both Bart and Posey in the lineup.

Heineman and Chadwick Tromp have been splitting time behind the plate for the Giants, but the pair have struggled to consistently produce so far this season. Giants catchers entered Thursday with a .496 OPS, which ranked 27th in the Majors, according to FanGraphs. The two rookies excelled at pitch framing, but they also endured growing pains in the form of four catcher interference calls.

As for McCarthy, when a player's contract is designated for assignment -- often abbreviated "DFA" -- that player is immediately removed from his club's 40-man roster, and 28-man roster if he was on that as well. Within seven days of the transaction (it was previously 10 days), the player must either be traded, released or placed on irrevocable outright waivers.

Bart should give the Giants a defensive upgrade at catcher, but Zaidi said he’s particularly eager to see how Bart fares against big league pitching. Bart batted .278 with an .824 OPS and 16 home runs over 79 games between Class A Advanced San Jose and Double-A Richmond in 2019.

“The defense is really good, but he's the type of guy who gets your attention when he's got a bat in his hands,” Zaidi said.