It remains to be seen if LeBron James will actually receive the rumored billion-dollar payout from his lifetime Nike deal—and if he does, it's speculated that it will happen long after he's retired from the NBA—but new basketball footwear sales figures suggest that the Swoosh may have bitten off more than it can chew.

The Street took a close look at Foot Locker's most recent earnings report and noticed that something that could have a major impact on the much-publicized deal: basketball sneaker sales are dropping, and the retailer says that LeBron's sneakers have been moving especially slow lately. 

"The Jordan business is exceptionally strong, while the Nike basketball business has been soft," a footwear industry analyst told The Street. "It's an item issue as [offerings from] Kobe Bryant, Kevin Durant and LeBron James did not do as well last year."

This news comes just days after LeBron's longtime business partner Maverick Carter told GQ that Nike "feels great about the deal."

Once the brand catches wind of these latest numbers, it might be singing a different tune.