The former Catalans' trainer believes the Argentine star to be the best player in the world and admitted a draw was a fair result in Sunday's Clasico
Two goals from Messi secured a point in the first Clasico of the new Liga campaign, as the Argentine attempts to surpass his previous records and win more silverware with the Catalan giants.
"Right now, there is no one that can compare with Messi," Rexach told La Xarxa.
"If you look at his numbers, nobody has scored more goals than him. He is setting some unusual records. He has won many titles. Finally, looking at what he has achieved, he will be the best.
"Messi has that gift of appearing and scoring a goal or giving an assist."
Rexach also spoke of El Clasico, which he believed to be a fair contest, with a draw being the correct outcome.
He added: "It was a match in which Messi and Cristiano Ronaldo did not interfere too much in, but they are players who at any time can make a difference.
"When you see the game, you think Barca could win, but Real Madrid had good chances. I did not want either team to lose, the draw was not bad for either of them."