David Beckham Says This Has Been the 'Biggest Challenge' of His Career (Exclusive)

• David Beckham reveals the "biggest challenge" he's faced in his career and why it's "the most rewarding"
• The soccer star talks about Lionel Messi's impact on soccer and Inter Miami CF
• Beckham tells PEOPLE how he believes soccer can grow its popularity in the United States

Soccer star David Beckham has faced many challenges throughout his illustrious career. 

A World Cup red card that resulted in global backlash, pressure to perform under intense scrutiny throughout his relationship with former Spice Girl, and now wife, Victoria Beckham, and his public struggles with Obsessive-Compulsive Disorder (OCD) to name a few. Still, none of these trials compare to Beckham’s current role as co-owner of Inter Miami CF soccer club.

“When we first announced it, I thought we’d have the team up and running in a few years,” Beckham tells PEOPLE at an Inter Miami CF Tailgate to introduce Ninja’s FlexFlame™ 5 in 1 Outdoor Cooking System.

But the process of building the fútbol club, the accompanying soccer academy for youth players and the now-under-construction stadium took quite a bit longer. “It’s been the biggest challenge that I’ve had in my career and my business life, but it's been the most rewarding," he says.

Related: David Beckham Celebrates His Milestone 50th Birthday with Stylish, Star-Studded Miami Party

One such challenge that has resulted in unimaginable rewards has been signing legendary player Lionel Messi to the team. “I always promised that I would bring the world's best players here, and when you make those promises — especially here in Miami — you have to keep it,” Beckham says, while sampling select grill creations from the La Familia fans. “But I never thought in my wildest dreams I would bring the greatest player to have ever played the game.”

The effect of Messi’s presence on the team is almost ...