Los Blancos sold the winger to Manchester United this week for €84 million but the Blaugrana ace says the capital club have just got rid of one of "top 10 players in the world"
The European champions could pocket a grand total of €84 million from the winger's move to Old Trafford, which was completed earlier this week.
However, Mascherano believes that his fellow Argentine will be sorely missed at the Santiago Bernabeu.
"It’s not an issue that concerns me but I think they’ve lost out,” Mascherano told Mundo Deportivo.
"He’s a player I like a lot. He’s among the top 10 in the world.
"He adds balance to attack and defend and has a great engine. You can use him in many positions."
Mascherano looked set to switch clubs himself at the end of last season, with Napoli having been hopeful of luring the versatile defender to the San Paolo.
However, after a stellar World Cup campaign, the 30-year-old ultimately signed a contract extension with Barcelona, much to Mascherano's delight, given that he did not want to endure a divorce as difficult as the one he went through with former club Liverpool.
“A relationship with a club is like a marriage," he mused. "The two sides have to get along. If in doubt, it’s better to talk about it and not come to the worst.
“I remember leaving Liverpool not as I would have liked and I would regret it for a lifetime if the same thing happened to me with Barca.
“The club sensed something at the end of the season. Obviously I’m very grateful I was told I could continue.
“Before the World Cup I had a short conversation [with coach Luis Enrique] that let me know they wanted me.”
Mascherano departed Anfield in 2010 in acrimonious circumstances, with the player having to publicly deny having refused to play in a game against Manchester City before his exit.