London Stadium before the St. Louis Cardinals and Chicago Cubs...

London Stadium before the St. Louis Cardinals and Chicago Cubs played in the MLB London Series on June 25, 2023. Credit: Getty Images

LONDON — For the first time, the Mets will play in Europe this weekend.

They departed the United States for the United Kingdom late Wednesday night, and on Saturday and Sunday will compete against the Phillies in the London Series — part of the renewed joint effort by MLB and the players’ union to stage more international events.

This is the third time MLB will play regular-season games in London, following Yankees-Red Sox in 2019 and Cubs-Cardinals in 2023. The Mets happen to have a pair of players who were involved in that first iteration: J.D. Martinez and Adam Ottavino.

With a little help from those two, here is what you should know going into the Mets’ very different few days, from the time change and the atmosphere to hitting in a soccer stadium and abroad-related technicalities.

“You gotta treat it as a business trip,” said manager Carlos Mendoza, a Yankees coach in 2019.

The time change can be rough — especially next week

The Mets took an overnight flight and were scheduled to land in England late morning Thursday, a day off. The advice to players from the team’s experts: For the sake of their sleep schedule and adjusting after the jetlag, power through and stay awake until nighttime Thursday.

Thursday is their only free day, with a workout and news conferences scheduled for Friday.

“You can’t sleep that day away,” Ottavino said. “That would be a waste anyway.”

In Ottavino and Martinez’s experience, by game time Saturday — 6 p.m. in London, 1 p.m. in New York — the five-hour time change is mostly fine. They’re running on adrenaline, Martinez said, so it’s not a huge difference.

The hard part comes next week, when they have to switch back to a normal routine and schedule. The Mets are off on Monday, then play Tuesday at 7 p.m. — midnight London time.

“I remember on the way back it was like, woah, dude, I didn’t account for this,” Martinez said. “The whole team was dead for four or five days afterward.”

Ottavino said: “I wasn’t over the hump for, like, a week after.”

That didn’t necessarily reflect in the teams’ records. The Red Sox, Yankees, Cubs and Cardinals went a combined 12-12 in the week after their respective trips abroad. For the Mets, that would be an improvement.

They’re playing in a soccer stadium

Originally built for the 2012 Olympics, London Stadium primarily is the home of West Ham United of the Premier League, the top tier of soccer in England.

That means a larger capacity — 60,000 people — than modern American ballparks.

MLB built a temporary baseball structure over the usual playing field, with dimensions that are smaller in some areas but bigger in others compared with Citi Field.

* Leftfield line: 330 feet (vs. 335 at Citi Field)

* Left-center alley: 387 feet (vs. 370)

* Centerfield: 392 feet (vs. 408)

* Right-center alley: 387 feet (vs. 380)

* Rightfield Line: 330 feet (vs. 330)

London Stadium is mostly covered, so wind shouldn't be a factor, Ottavino said. The artificial turf played fast, in his experience, which means more ground balls that sneak through for hits, more gappers that get to the wall for extra bases.

The atmosphere is awesome

The previous London Series drew huge crowds — about 59,000 per game in the first go-around, 55,000 last year.

The funky part: It’s not a home crowd. It’s “a jumble of English people and some people visiting,” as Ottavino put it. So the majority of fans largely didn’t care about a specific team. They just cheered for action.

That made for a “way more” intense vibe than a typical regular-season game, Martinez said.

“They don’t even know what they’re cheering about. It’s funny,” he said. “But it’s cool. For people who really haven’t played in big games and stuff like that, you’ll get a close experience of what it’s like . . . The atmosphere is great. It’s like you’re playing in a World Series.”

The offensive environment should be … normal?

You might remember that when the Red Sox and Yankees played in 2019, it was 6-6 after the first inning. They combined for 50 runs across two games.

The Cubs and Cardinals had much more normal outputs — 9-1 in one game, 7-5 in the other.

MLB’s stance is that the offensive environment shouldn’t be much different than it is stateside.

“We were freaking out,” Ottavino said of that 12-run first inning. “It seemed like everything was a hit. It seemed like our balls weren’t moving the same and all that, but then they looked at the data and there was no real evidence of any of that [abnormal ball movement] . . . It was a one-off. You can’t make a lot of concrete [conclusions] off two games.”

It’s more than just London

The London Series is part of what is branded as the MLB World Tour, the terms of which were negotiated by the league and players as part of the 2022-26 collective bargaining agreement (the deal that ended the lockout).

Already this year, for example, MLB has played games in the Dominican Republic (spring training), Korea and Mexico. Next year, Japan and Puerto Rico are on the agenda.

A perk for the players: MLB pays each of them a $70,000 stipend for participating in an in-season European, Asian or Australian venture (or $20,000 for Latin America).

The international trip comes with other technicalities

The Mets and Phillies are allowed a three-man taxi squad. For the Mets, that will be third baseman Brett Baty, catcher Joe Hudson and reliever Cole Sulser.

They are allowed to add one of those position players — Baty or Hudson — as a 27th player on the active roster. The others will be present as guys they can call up if needed without dealing with the otherwise impractical logistics.

Each team will be the home team once — the Mets on Saturday, the Phillies on Sunday.

If you’ve done it once…

In separate interviews, Ottavino and Martinez said they weren’t looking forward to the trip.

The novelty isn’t there anymore, having done it before. The whole thing ends up being kind of exhausting. Martinez said it would be easier if it happened at the start of the season, which is how MLB handles series in Asia.

Many of the rest of the Mets, some of whom have never visited England, indicated significant excitement.

“That’s OK. I’ll make the most of it,” Ottavino said. “Just because I already did it. The logistics of it — customs, the travel, the time change. It’s more of an inconvenience to me at this point, when I’m very routine-oriented, so I have to figure out how to thrive through it. It’s fine. It’s a challenge.”

Martinez said: “It’s cool because people are very excited about it. You don’t want to rain on their parade. But it’s tough. It’s tough.”

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