CHARLOTTE, N.C. (WNCN/AP) — The labor group that represents NFL players is filing a grievance about the playing field in Charlotte at Bank of America Stadium, an ESPN report said Sunday.

The NFL Players Association filed the grievance after complaints by Detroit Lions players about the hardness of the playing surface during a game last weekend in Charlotte against the Carolina Panthers.

In the past, several Carolina players have complained about the synthetic surface at the stadium.

Detroit’s Jared Goff joined that chorus after a December 24 game, which the Panthers won 37-23.

“I thought the field conditions were below NFL level standard, specifically pregame,” Goff said. “It warmed up as the game wore on. I don’t what the deal is here. But they need to figure out a way to make the field not feel like cement. Why that is, I don’t know.”

ESPN reported the NFL players’ group complained about the field conditions before the game last weekend.

D’Onta Foreman and Chuba Hubbard both exceeded 100 yards rushing in the first half of the Christmas Eve game as the Panthers built a 24-7 lead.

Both running backs said they felt at times the Lions didn’t even want to tackle them on Carolina’s unforgiving artificial turf.

“Definitely,” Hubbard said. “We pride ourselves on just wearing on a team, and when it gets cold out here like this, not too many people want to get hit or do any tackling — and that definitely showed.”

The Panthers media office later reported the game on December 24 — at 20 degrees — was the coldest for a home match in Carolina franchise history at Bank of America Stadium.