Louis Rees-Zammit has emerged as a fitness doubt for the Kansas City Chiefs’ pre-season game against the Detroit Lions.

Former Wales and Gloucester wing Rees-Zammit is targeting a place in the Chiefs’ 53-man roster for the NFL season, which they begin by tackling the Baltimore Ravens on September 6.

But the 23-year-old missed training on Wednesday, with the Chiefs assistant coach Dave Toub telling reporters Rees-Zammit might not be available for Saturday’s clash and confirming a back injury.

The Chiefs’ final pre-season fixture is against the Chicago Bears next week, after which their squad will be announced.

Rees-Zammit quit rugby union in January to pursue a new career in American football.

He subsequently signed a three-year deal with the reigning Super Bowl champions and performed as running back, kicker and kick-returner in the Chiefs’ opening warm-up match against the Jacksonville Jaguars, in addition to being part of the punt coverage team.

“It was a great first experience,” Rees-Zammit told the Irish NFL Show following the Chiefs’ 26-13 defeat at EverBank Stadium in Florida.

“I loved it, I loved getting the snaps I did, on special teams as well which was great. I’ve just got to look back on this, review it and see how I can get better.”