Messi has been a constant tormentor to Madrid in the El-Clasico in recent seasons and playmaker Xavi is backing the Argentine superstar to deliver the goods once again at the Santiago Bernabeu.
"Leo will always make the difference," the Spain midfielder is quoted as saying by his club's official website.
"He's usually a decisive player and he's someone who grows with these games and likes playing in these games."
While Messi has been receiving the plaudits for his superlative displays against the nine-time European champions, Cristiano Ronaldo has often flattered to deceive in matches against the Catalans.
Nevertheless, Spanish World Cup winning midfielder Xavi feels that the criticism dished out to Ronaldo is a tad unfair.
"Strikers do have runs of scoring and sometimes they dry up," he explained.
"It's something a player gets used to - especially goal-scorers."
Xavi also paid tribute to midfield partner Sergio Busquets, claiming that the Barcelona youth product is a true unsung hero for Pep Guardiola's side.
"He should have been in the FifPro World XI," he argued. "He's an extraordinary player and he rarely makes a mistake either in attack or defense.
"He gives us balance and is key to our system. He's more valued by his fellow professionals than by the media."