The World Cup is one of the few titles that continues to elude Messi, with fans in some corners asserting that the 31-year-old cannot be named the greatest of all time unless he lifts the famous trophy.
The Rosario native did come close in 2014, however, taking Germany all the way to extra-time in the final in Brazil, but it was Die Mannschaft who would emerge victorious after Mario Gotze's dramatic strike separated the sides.
And with the Albiceleste coming up short despite having their talisman in the team, Mertesacker revealed Germany's gameplan to keep one of football's best ever players quiet for 120 minutes.
“If Messi has the ball, he is fantastic to watch and difficult to stop,” Mertesacker told DAZN. “You have to double up on him, triple up on him even, stay with him constantly to block his way to the goal.
“Never tackle, never go down, we've heard it over and over again. You have to try to keep Messi away from the goal and block him with multiple players while being as close to him as possible. He is too quick, too fast, too intense with the ball.
But despite the 34-year-old's admission that the Argentine must be escorted closely at all times, he did point out that centre-backs should stand their ground as leaving their post to chase down Messi only creates space for other attackers.
“You need good communication between the lines – I'd have to say to the number six 'Sorry, but now you have two opponents',” Mertesacker went on.
“In Argentina, they have never managed to combine the strengths of their defence and attack. The attack does their thing and the defence does their thing. We've [Germany] always managed to do that very well.
“You just get the feeling Messi never had full control. He won the trophy for the best player but not for the best team. [Not winning the World Cup] is maybe the only thing you can hold against him.”