During the 2022 season, ESPN published data supplied by the NFL that purported to show that injury rates on grass and artificial turf were approximately the same. The NFL Players Association says that data was misleading, and that the NFL highlighted one outlier year’s worth of injury rates when the full body of research makes clear that players are injured more often on artificial turf.

According to the NFLPA, the NFL selectively released injury data from 2021 only, and 2021 happened to be an unusual year because injury rates on artificial turf and grass were very similar that year — although even in 2021, players were slightly more likely to be injured on turf. But in every other season besides 2021, the NFLPA says, injury rates were significantly higher on turf.

That includes the 2022 season, when injury rates on turf were as high as ever — and when the NFL didn’t make an effort to get those injury rates published by the media.

NFLPA President J.C. Tretter wrote on the NFLPA’s website that the injury data from the 2022 season makes clear that 2021 was a statistical outlier, and that in every other season for which there is injury data to compare grass and turf, grass has proven significantly safer.

“In short, last year, the gap – much like the NFL’s credibility with players on this issue – was as wide as it has ever been, proving that (as the NFLPA suspected) 2021 was in fact an outlier,” Tretter writes. “Now, 10 of the previous 11 years show the same exact thing — grass is a significantly safer surface than turf.”

Tretter said the players can’t trust the NFL when it would selectively release misleading data on players’ health and safety.

“The credibility the league has with the players on health and safety issues is virtually nonexistent,” Tretter writes. “Instead of following the long-term data (which is clear on this issue), listening to players and making the game safer, the NFL used an outlier year to engage in a PR campaign to convince everyone that the problem doesn’t actually exist.”

The union would prefer that every NFL stadium have a grass field, but it making little progress in convincing the league to take the issue seriously. In fact, this year one more stadium will have a turf field, as the Titans have announced that they’re replacing their grass with an artificial surface.

The turf at U.S. Bank Stadium will be replaced in early 2024 with a monofilament surface that has been shown to carry slightly lower injury risk than the version of artificial turf currently in the stadium.

Minnesota Sports Facilities Authority approved turf replacement at its regularly scheduled monthly meeting Thursday, which also included a cost estimate and new renderings for the second phase of the stadium's enhanced security perimeter.

The slit film-style turf like that used at U.S. Bank Stadium has been under scrutiny since the end of last season, when NFL and NFL Players Association data showed it has a higher rate of non-contact leg injuries than other types of artificial surfaces used around the league.

U.S. Bank Stadium, which opened in 2016, was one of three stadiums left in the NFL to use slit film turf. The surface gained further attention on Oct. 8, when Vikings star receiver Justin Jefferson suffered a serious hamstring injury against the Kansas City Chiefs that put him on the sidelines for much of the season. Chiefs tight end Travis Kelce sprained an ankle on the turf in the same game.

"It was a freak accident," Jefferson said in November after returning from his injury. "I felt pretty good going into the game. I didn't really have any hamstring problems; a little tightness, but not really something to be worried about. It just happened. Bad timing, bad positioning. I also have to look at my technique, also. Just having my feet under me, and not getting into those types of situations. [The turf] could have had a slight issue, but I'm not going to blame it on turf."

In November 2022, the NFLPA wrote an open letter calling for the slit film turf to be banned at six stadiums around the league, after Packers pass rusher Rashan Gary tore his ACL at Ford Field in Detroit. The Saints, Jets/Giants and Lions removed their slit film turf after last season, leaving just three teams — the Vikings, Colts and Bengals — with that surface in their home stadiums.

By 2024, with the Vikings and Colts scheduled to replace their fields, the Bengals' Paycor Stadium, where the Vikings played last Saturday, will be the only remaining slit film field in the NFL.

Vikings executive vice president Steve Poppen said that monofilament turf generally provides a "slightly better safety experience." He and MSFA chairman Michael Vekich said the replacement plan began last summer before Jefferson's injury. The current playing surface was installed in 2019, and its warranty was expiring after this season.

The MSFA, which oversees the state-owned building on behalf of the public, chose Austin, Texas-based Act Global to install new turf at U.S. Bank Stadium in early 2024 for $1.3 million. The company had previously installed new turf at the stadium four years ago. Money to replace the turf comes from an existing MSFA capital account that is funded by both the state and the Vikings for routine maintenance at the stadium.

The Vikings' player health and performance department led much of the research on the choice of the new turf, which will also be installed in the team's indoor practice facility at the TCO Performance Center in Eagan. Poppen said the team will pay for that turf replacement.

This will be the second time the turf has been replaced at U.S. Bank Stadium, which has played host to eight NFL seasons as well as soccer, high school football, collegiate baseball, the men's college basketball Final Four, and Garth Brooks, Taylor Swift and Metallica concerts. Because of the turf replacement, the Gophers baseball team will not be able to play at the stadium early next year.