Their grass is showing.

The artificial turf field at MetLife Stadium was replaced by a natural grass playing surface in advance of this summer’s World Cup.

The project — encompassing years of R and D and an early May install — was designed to take the maligned home field of the Giants and Jets and make it fit for a procession of visiting soccer superstars and eventually the World Cup final, which is set for the venue (New York New Jersey Stadium in the official parlance) on July 19.

But that grass field received a string of salty reviews — yellow cards, if you will — from the first teams to play at the Meadowlands in the group stage of the World Cup.

“Well, the pitch was … I don’t know if I’d even call it that,” France’s Adrien Rabiot snarked after last Tuesday’s tilt against Senegal. “It seemed more like an artificial pitch. It was hard and rigid, but it’s like that for every team. … I hope we find better pitches in our other games.”

France manager Didier Deschamps called it a “special surface,” not in a nice way.

“We need to get used to this,” he said. “There might be some cement below the grass. You have very short shards of grass here.”

Part of the World Cup’s grass mandate, which affected eight stadiums across North America, is due to the different conditions optimal for soccer — the beauty in the beautiful game involves the ball rolling and skipping over the pitch in a certain way — as opposed to American football.

“Because of the weather and the heat, the grass dries out quickly and the game ends up being very slow,” Brazil superstar Vinicius Junior said after his team opened its tournament with a draw against Morocco at MetLife. “We want to move the ball from one side to the other, and this disrupts our game.”

The threat of injury also looms in the background of the MetLife surface swap.

The stadium’s turf has been blamed in recent years for Aaron Rodgers tearing his Achilles and Malik Nabers tearing his ACL, to name two prominent examples (though catastrophic football injuries happen on grass as well).

No one, from tournament organizers to the club teams that employ the players with nine-figure transfer values to the fans who paid through the nose to attend, wants to see anything like that.

“The pitch in New York was really tough — it took a lot out of the players’ muscles,” Deschamps said this week.

Monday night’s 3-2 win for Norway over Senegal — under gray skies that had covered the region in heavy rainfall during the day — was the third of eight matches being hosted at MetLife.

Third down, goal to go.

The feedback after this one was apparently improved. The extra moisture seemed to help.

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“My players like when it’s been watered,” Senegal coach Pape Thiaw said. “There was rain today, so it’s a good thing for the pitch. My players didn’t complain.”

Norway’s Fredrik André Bjørkan told The Post the field was “a little bit harder, the ball moves a little different.” But the Norwegians, hailing from northern climes, are used to peculiar surfaces.

“We played on artificial grass our whole youth, so for us, no problem,” Patrick Berg said. “Good footballers, with good technique, they handle the surface.”

As kickoff approached Monday in East Rutherford, there were just a few slightly discolored patches of grass visible from above.

“The pitches at all 16 FIFA World Cup 2026 stadiums remain in excellent condition from both a playability and player safety perspective,” FIFA said in a statement shared with The Post. “While there have been comments regarding the visual appearance of certain areas of the playing surface at NYNJ Stadium, FIFA’s Turf Management Team’s assessment is that every pitch is healthy and performing as intended for elite competition.”

MetLife’s grass mostly needs to be ready for the global showcase of the final, in a little less than four weeks’ time. Until then, they’re playing the lawn game.