'You're always paying attention': What it's like to mark Lionel Messi

"You prepare differently for these games [against superstars like Messi] because you know there's no time for a mistake," Leibold said.

Leibold made his mark on the offensive side of the field in the sixth minute of the match, taking the ball from Miami's Marcelo Weigandt just across midfield. He took the ball to the top of the box before dropping a pass off to Erik Thommy, who netted the opening goal. 

Leibold made an excellent play, but Messi's presence might have influenced him to not push up as far as he might like for fear of not being able to recover should Miami find itself on the attack.

"Messi being on my side impacts my decision-making 100%," Leibold said. "Great players like Messi know exactly where the space is. When they win the ball, they find the space and know exactly what the next step is. They are the best in the details and they're one step ahead. That's the biggest difference between him and your average player."

In the 27th minute, Leibold had Messi in front of him as Miami brought the ball down the left side. A pass came to Messi at the top of the box and Leibold quickly stepped up to pressure the Miami star, resulting in a saved shot. 

A moment like that illustrates Messi's brilliance — he flashes into space and within less than a second of receiving the pass he puts a shot on goal. If Leibold didn't step up as quickly as he had, it could have resulted in a goal.

"You always have to be aware of what he's doing next," said Leibold. "He's just walking. He's not like every other striker or winger who makes a lot of movements. With him, you don't know what he's going to do and that makes him so difficult to defend."

Messi affects the defense simply by being on the field. Whether he's near the ball or 50 yards away, he causes defenders to tighten up and question what they're able to do. Can they push up as far as usual? Can they join the attack? All these questions cause a defense to perhaps be more timid than it normally would be.

"You're always paying attention to where he's at," said Leibold. "Even when we're attacking, you're watching him and wondering where is the channel for him when they win the ball back. He changes the game for his team, but he definitely changes the game for the other team."

For Leibold and other MLS players, they've seen up close what Messi and fellow Miami striker Luis Suarez can do. The fact that both players are in the twilight of their careers hasn't diminished what they're capable of on the field. 

Leibold wonders how teams in La Liga, the premier Spanish professional league, defended against Messi and Suarez's FC Barcelona clubs, where they spent six seasons together.

"We were talking after the game," said Leibold of his teammates. "Imagine you have [Andres] Iniesta, you have Neymar, you have Messi, you have Suarez. So there's not just one guy. There's like four or five guys you have to constantly be paying attention to. You have to be locked in or you stand no chance."

For Leibold and fellow MLS defenders, the challenge of marking Messi is the challenge of a lifetime — one they won't soon forget. Unless Sporting KC, now in 12th in the Western Conference, makes the playoffs, Leibold won't play Messi and first-place Inter Miami again until next season. Whenever that next meeting comes, Leibold will be paying attention. 

"You just have more respect for guys like Messi and Suarez," he said. "They could be quiet for 87 minutes and then they have two unbelievable touches that can decide the game for their team."

All quotations obtained firsthand unless otherwise noted.