ESPN: Chiefs favorite RB ruled out for the season due to injury.

Due to a back ailment, the former Wales wing is questionable for the Chiefs’ preseason game against the Detroit Lions on Sunday.

The NFL champs will then play the Chicago Bears in their final preseason game before selecting their 53-man roster for the upcoming season.

After participating in many positions in Kansas City’s first preseason game against the Jacksonville Jaguars, Rees-Zammit was praised.

At a training session on Wednesday, the 23-year-old was spotted stretching his upper body with coaches while not donning a helmet or pad.

As he stated that his players needed to improve on their kick returns in light of new rules and errors in their first game against the Jaguars—one of the crucial tasks Rees-Zammit is anticipated to take on—Chiefs special teams coordinator Dave Toub revealed the back ailment.

“We just need to get more reps out there and make sure it’s clear what the rules are,” Toub said.

“We clearly made a mistake during the match. Even though it ultimately cost us, we learned a lot from it.

“Those are going to be the same guys you saw. I still want to see guys, though. Although [Rees-Zammit] didn’t practice today, I still want to see him. He might not be accessible. I want to see a lot of guys, so we’ll see. But, I still want to see. We have time to complete that.”

In addition to playing punt coverage, Rees-Zammit saw action as a running back, kicker, and kick-returner in Saturday’s 26–13 defeat at EverBank Stadium in Florida.

In the end, he had one yard on two carries, three yards on one reception, and one special teams tackle.

The Chiefs, the defending NFL champions, will announce their roster on August 27 in advance of their September 6 season opener against the Baltimore Ravens.