That's because Barnes - who moved from Golden State to Dallas earlier this month - is one of three players on the team who isn't sponsored by Nike.
Barnes and Kyle Lowry - who is standing third from left and has his entire lower half covered up by Jimmy Butler - wear Adidas footwear, while Klay Thompson (fourth from right, behind Anthony and DeAndre Jordan) is sponsored by Anta.
If you thought Nike was going to let rival brands encroach on their team photograph you had another think coming.
It's not the first time the sports apparel giant has pulled a move like this either. In 2008, Nike had the team headed for Beijing line up in reverse height order so coach Mike Krzyzewski could block the Adidas sneaker of Dwight Howard.
Technically, Dwyane Wade's Converses were in the shot too, but Nike has owned Converse since 2003 so let it slide.
A similar situation occurred before the London Olympics in 2012. The choreography of the shoot was made easier by the fact only one of Team USA's 12-member squad - Kevin Love - wasn't a Nike athlete.
Love still wore Nikes in games (citing a "comfort clause" in his contract with a Chinese shoe company) but was still kept well hidden in this team photograph.
SB Nation's Tim Cato has suggested Nike's influence on America's national basketball teams runs even deeper. "There's speculation that Candace Parker, the best player on the best team this season in the WNBA, and one of the most famous female athletes of this generation, was left off this year's Team USA women's squad in part because of her Adidas shoe deal," Cato wrote.
"There were other reasons you can point to, but that it might have even been a small factor is incredible."
You don't become a $100 billion company without worrying about the details.