CHICAGO -- The playing surface at Soldier Field was the subject of criticism throughout the Bears' 19-14 preseason win over the Kansas City Chiefs on Saturday.

Filled with noticeable divots and patches of missing grass, the field conditions became so noticeable that JC Tretter, the president of the NFL Players Association, took to Twitter to question why the league allowed Bears and Chiefs players to perform on a surface in such a poor visible state.

"The NFL said that this field met minimum testing standards," Tretter tweeted. "We clearly need to re-evaluate what is an acceptable surface for players to compete on. We need new testing metrics looking at the performance and safety of every field. The NFL can and should do better."

The Bears hosted their lone game of the preseason eight days after Elton John played a concert at Soldier Field, which left the grass visibly damaged with lines of missing turf spanning the length of the field. The Chicago Fire, who also play at Soldier Field, announced before the concert that they were moving their Aug. 21 game to nearby SeatGeek Stadium "due to the expected field condition at Soldier Field from a series of planned events at the venue."

"I'm new here so I don't know the situations, but I know the guys are trying to do their best, and the playing surface was passed by the NFL for us to be on," Bears coach Matt Eberflus said. "I thought it was firm and it was good, so that's where we'll leave it at."

The Bears held their annual family fest practice at Soldier Field on Tuesday, and while the playing surface was still visibly damaged, some players say the field conditions Saturday were better than earlier in the week.

"I mean, it's kind of always been like that," quarterback Justin Fields said of the turf issues. "It definitely was better than the family fest earlier this week. I'm just glad it was better than it was earlier this week because it wasn't the best. The grass could definitely be better for sure."

Last week, Bears kicker Cairo Santos lamented that the field conditions at Soldier Field have forced him to adjust how he trains during the offseason to emulate the challenges he faces with the turf during home games.

"I was training in Florida in Jacksonville and I was going to a turf field at a high school, which was perfect," Santos said. "It was almost like, 'OK. I'm getting too comfortable.' So in my neighborhood, there's a soccer field and the grass is a Bermuda grass. It's real long. I was like, 'OK. This is more like it.'"

Santos added, though, that he has "seen better. It's just what we have to deal with."

Soldier Field is the oldest stadium in the NFL with the smallest capacity. Last September, the Bears took a step toward leaving their historic home when they signed a $197.2 million purchase and sale agreement (PSA) with Churchill Downs Inc. for the 326-acre Arlington Park property in suburban Arlington Heights.

The Arlington Park site, which is 30 miles northwest of Soldier Field, is anticipated to be the site of a new stadium for the Bears in the future.