He also had no clue that he would end up playing all 14 innings and giving the signals for each and every one of the 213 pitches that eight Mariners pitchers threw in the game.
But Moore did all of that, and he was all smiles after the Mariners' come-from-behind 4-3 victory over the White Sox before 16,366 at Safeco Field.
Just when it appeared Seattle would lose the game and the series, facing a two-run deficit entering the ninth inning against Sox closer Bobby Jenks, Jose Lopez and Bill Hall hit solo home runs to get the Mariners even.
Ichiro Suzuki's second walk-off hit of the season, a line-drive single into right-center field off Sox right-hander Scott Linebrink, scored Ryan Langerhans from second base with the winning run.
It was the Mariners' 12th walk-off win of the season, tying a franchise record, and their 76th win overall. Ichiro ran all the way into center field before being caught by his teammates.
Though he was removed for pinch-hitter Kenji Johjima in the 14th inning, Moore caught a complete game.
"It was a blast, and something I will never forget," he said. "It was awesome."
It also had to be one of the longest Major League debuts for a catcher.
"I thought Adam Moore did a phenomenal job today," Wakamatsu said. "The one thing that's probably a little hard, and people don't understand, is how many guys he caught for the first time in that ballgame. It's not an easy task. I thought he did a great job, did a great job of calling and I'm really happy for him.
"You're always going to remember your first game in the big leagues, and he will remember this one."
Moore, who joined the Mariners last Sunday, the day after Triple-A Tacoma was eliminated from the Pacific Coast League playoffs, started Thursday's series finale primarily because he caught right-hander starter Brandon Morrow in the Minors.
"We talked about trying to get guys some playing time before the year's out and we just thought this was a good opportunity with [Morrow] starting today," Wakamatsu said. "They both have maybe a little bit better comfort level."
Morrow had some control issues, walking six batters in 5 2/3 innings, and surrendered six hits. But he allowed just three runs and make big pitches when he had to. The game was turned over to the bullpen, which played a major role in the outcome.
Seven relievers collaborated on 8 1/3 scoreless innings, allowing just four hits and five baserunners.
"Thank God it's September and we have some arms down there," Wakamatsu said "They did a phenomenal job."
Moore had never caught either Mark Lowe or David Aardsma, but by the time they entered the game in extra innings, the catcher was fully into his game mode.
"I started relaxing around the third or fourth inning, knowing it was just a baseball game," Moore said. "Early on I was nervous. I was joking with [Rob Johnson] on the bench and told him I was feeling exhausted in the fifth inning. It was a great time, a great win and I couldn't ask for anything better."
Well, he was a bit bummed about the ball he drilled on one hop to shortstop Alexei Ramirez, who made a nifty catch and on-target throw to first base.
"I thought I had it, but he made a great play on it," Moore said. "Things happen. I didn't get my knock this time, but there's always tomorrow."
Moore went 0-for-5 before being pulled for a pinch-hitter, but as far as Wakamatsu was concerned, that didn't take anything away from the young catcher's debut.
"He didn't drop any baseballs," the skipper said. "That's a big thing. It sounds simple, but if you haven't caught guys and you're not accustomed to the movement of the pitch, that's tough to do. I thought he blocked the ball and really, for me, had a good comfort level back there.
"I didn't see a young kid that was real nervous back there. He did a good job of taking trips to the mound, especially with Brandon. I thought he worked him through and got the best he could out of him."
Morrow keeps showing flashes of brilliance, but he still hasn't been able to command his pitches for more than an inning at a time.
"The story has been the command and the walks," Wakamatsu said. "If he eliminates those ..."
Two of the six batters who walked scored runs and also hiked Morrow's pitch count.
"Stuff-wise, I thought his stuff was good," Wakamatsu said. "It's just the education of learning how to pitch after a little bit. It's hard to say whether it's command or being tentative. The amazing thing is he doesn't get hit and that's kind of a credit to the stuff he has. The rest is just being aggressive and going at hitters and it's a learning process."
Sox starter John Danks was just the opposite of Morrow, showing precision as he held the Mariners to one run over eight innings -- a solo home run to Adrian Beltre in the seventh.
And then came the ninth, and the Mariners' latest Houdini act.
"It was 2 1/2 hours of satisfaction and then 2 1/2 hours of [bad] baseball," White Sox manager Ozzie Guillen said. "Go and ask [the players]. I don't have any more quotes, seriously. What am I going to say? They [are bad]? Yes, they are."
The mood in the other clubhouse was far different.
"It was a great series win, first and foremost," Wakamatsu said. "For us to battle the way we did with our backs to the wall and hit two home runs to tie this ballgame was unbelievable."
Jim Street is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.