LONDON — The NFL is ready to become the first U.S. sports league to play a regular-season game in China.

The reason it may not happen as planned stems from what may happen afterward to the two participating clubs.

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“The main focus of the work now is as much about how does a team come back from China and then play and be competitive after a trip like that,” NFL executive vice president of international Mark Waller told Sporting News in an exclusive interview. “It’s less of the focus on the game in China itself.”

Media reports surfaced earlier this year that the Los Angeles Rams were expected to play their 2018 season-opener in Beijing. The Sports Business Journal reported in July that San Francisco was the expected opponent.

The NFL responded that nothing was definitive. And based upon Waller’s comments, that still rings true.

The biggest logistical challenge is the distance between the U.S. and China. The estimated flight time from Beijing to both Los Angeles and San Francisco is roughly 12 hours.

“The last thing you want to do is have two teams go to China, play a game and find the travel, time zones, and body shifts that go on make you end up not being able to be at your competitive best when you come back,” Waller said.

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One option would be playing the game before the traditional Thursday night opener to give extra time for a return. But that creates its own set of challenges about when teams would leave the U.S. for China and the impact the departure date would have on traditional preseason scheduling such as the fourth exhibition game and final roster cuts.

“It’s almost certainly going to have to be a game early in the season because the idea of going through a whole season and then making a trip like that toward the end is probably at the moment a step too far,” Waller said. “What we’re looking at is potentially an early game in-season before the bye weeks [NFL byes run from Weeks Four to 10].

“How do you go to China, play a game, come back and play the following weekend? How do we make that work?”

The NFL may not be able to, which wouldn’t be the first time plans to play in China were scuttled. The league postponed a 2007 preseason game between New England and Seattle until 2009 before canceling the contest entirely.