Bayern Munich centre-back Jerome Boateng believes Lionel Messi and Cristiano Ronaldo can smell a defender's fear in one-on-ones.
Real Madrid star Ronaldo and Messi have scored 63 goals between them for their clubs this season, with the latter's combination with Luis Suarez and Neymar at Barcelona drawing praise.
Boateng gave an insight into what it was like coming up against the world's best and how they capitalised on scared defenders.
"With Ronaldo or Messi, whatever option you choose is difficult if they come at you with open space. They're just so fast," he wrote for The Players' Tribune.
"Neymar and Messi are low to the ground and can turn quickly, so it's difficult for defenders like me, who are tall centre-backs.
"Ronaldo, he's got the height, but he's also got incredible speed, strength and a good header. You can't be lazy or caught on your heels with those players, because they will win and they will score.
"They are just too good for you to make even a little mistake. More than speed or technique though, as a defender you need confidence.
"Ronaldo, Messi, Suarez, Neymar - they can all smell if you're afraid to duel with them. One whiff and then they destroy you. So you gotta show up."
Boateng said the key to defending against the likes of Ronaldo and Messi was making decisions immediately.
"You have to assess the tactical situation. Quickly," he wrote.
"Am I covered, with my other defenders on my back? If I have cover, I can risk going for the ball in a duel or tackle.
"But if I'm the last man on the line, I can't risk a tackle. I need to do whatever I can to slow the ball down by using my positioning, hoping I can buy time for my team-mates to track back."