ST. PETERSBURG, Fla. — Max Scherzer’s next scheduled pitch in a game will occur in the first one that counts for the Mets this season. 

Spring training concluded for the team’s co-ace Friday as he departed the mound after throwing pitch No. 100 against the Rays.

Hours earlier, the Mets officially announced what The Post reported last week, that Scherzer will start the March 30 season opener in Miami. 

“It’s a heck of a day to pitch on,” said Scherzer, who started six openers for the Nationals. “The atmosphere is crazy in every single venue that you’re in. It’s going to be a great day.” 

Tylor Megill was the Mets’ Opening Day starter last year, after Jacob deGrom began the season on the injured list and Scherzer, who had sustained a minor hamstring injury late in spring training, needed extra time to prepare for his first start. 

Manager Buck Showalter also confirmed — as The Post first reported — that Justin Verlander will pitch the home opener on April 6. That start will occur after his Mets debut in Miami in Game 3. 

Showalter hinted he’s leaning toward a five-man rotation to start the season (team brass has considered the possibility of six starters for the first turn through), but said a plan won’t be finalized until he speaks with pitching coach Jeremy Hefner on Saturday. 

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Megill and David Peterson, who are competing for the rotation spot created by Jose Quintana’s absence at least into July after rib surgery, both are scheduled to pitch Saturday against the Cardinals. 

On Friday, Scherzer fired six innings at Tropicana Field and allowed two earned runs on four hits with 11 strikeouts and one walk.

Though many pitchers scale back for their final start of spring training, the right-hander built up his pitch count because he wants to ensure he’s ready to work deep into games from Day 1. 

“Now I am physically built for 100 pitches,” Scherzer said. “You can do whatever you want in spring training, it’s not real. You get to a regular season game, it’s much more intensive than a spring training game. But when you get into your opening day start and get into that 90-plus pitch count, now I can tell Buck: ‘Look, I’ve been here, I’m strong, I can go,’ or ‘Hey, I know where I’m physically at and I am starting to fatigue.’ ” 

Scherzer went 11-5 with a 2.29 ERA in 23 starts for the Mets last season after he signed a two-year contract worth $86.7 million.

Scherzer was twice placed on the injured list last year with oblique strains. 

But the Mets will enter this new season without lingering concerns about Scherzer’s oblique. 

“Just a different form of preparation,” Showalter said. “Max is always chasing another reason to give him and us a chance and that is why he’s so respected: everything is about winning.

“It’s a lot of fun shaking his hand after a good outing. He is fun to watch.” 

Scherzer spent much of this spring toying with the nuances of the pitch clock and said he is comfortable with MLB’s new timing device, which gives pitchers 15 seconds to start their deliveries with nobody on base and 20 seconds otherwise. 

“I never thought this was going to affect me,” Scherzer said. “You are never going to call a ball on me. It’s never going to be a result of me. I’ve seen it and it’s what I have thought: I would at times be able to pitch quick and other times pitch slow and something I could use to my advantage. The biggest adjustment has been on the hitter — hitters are now in the box ready. They are just not stepping out of the box.”