Dre Greenlaw has been a crucial part of the San Francisco 49ers defense in their Super Bowl run, but as of this article's writing it appears he may be out for the rest of the evening, leaving with an injury in the second quarter.
Greenlaw, running onto the field after a change in possession, appeared to suffer a lower leg injury and went down to the ground. After he went down, the team brought him into the medical tent on the sideline and it was reported as an Achilles' injury.
We don't know details from the team yet, but injuries to that tendon typically don't force you to come off the field unless they're serious. It's not a "bumps and bruises" part of the body, generally. It tends to be all or nothing.
Any injury in the NFL these days tends to be backdropped against the NFL's playing surfaces. Last year's Super Bowl featured a noticeably slippery field that was discussed by fans during the game and players afterward.
In the regular season, some fields, like MetLife in New Jersey, became unfortunately notorious for claiming ailments. Many players have become outspoken against the use of artificial turf, claiming it creates a significantly higher injury risk than natural grass. The general belief is that grass has more give than turf, but the data is mixed.
Did playing surface have anything to do with Dre Greenlaw's injury?
As with any injury, especially on a big stage like the Super Bowl, the playing surface will be questioned.
First, let's be clear: It's rightly impossible for us to say from afar if the playing surface played a role at all in the injury. Even the doctors and player, working with the injury up close, can't say for certain if the playing surface had anything to do with it.
The next question is whether the surface was turf or grass. The answer is it's grass. While it's an indoor stadium. Allegiant Stadium uses a rolling tray system that gives the grass sunlight outside, then they roll it in for games.
Injuries can almost never be isolated to just one variable like the playing surface. An accumulation of wear and various individual factors all play into it.