Sergio Ramos snubbed Lionel Messi when naming the toughest opponent he faced in his career

Sergio Ramos opened up on the player that was "virtually unstoppable" to stop as he discussed the toughest opponent of his trophy-laden career in football.

The 39-year-old former Spain international, who currently plays for Liga MX side Monterrey, had the unenviable task of coming up against some of all-time greats during an unforgettable 16-year spell at Real Madrid.

He previously named former Ajax, Inter Milan and Barcelona striker Zlatan Ibrahimovic as one of his standout opponents when he was asked to recall his three toughest opponents during a Q&A session in 2016.

"Ibrahimovic caused a lot of trouble with his size and holds the ball up well," Ramos said. "He plays great with his back to goal and was fast."

Ramos, a four-time Champions League winner, also named another former Barcelona striker, Samuel Eto'o, as one of his toughest but the player who ranked above them all was Ronaldinho.

In fact, when asked to name his toughest opponent, the former Los Blancos centre-back has name-dropped one of Brazil's greatest players on multiple occasions.

"For me, the most unstoppable is Ronaldinho," he said, as quoted by Telegrapfi. "At his best, hardly any defender could stop him."

Ronaldinho, who joined the ranks at Barca from Paris Saint-Germain in 2003, would win two La Liga titles and the Champions League with the Catalan giants, and often produced moments of magic on the Camp Nou stage.

He would go on to play for AC Milan, Flamengo, Atletico Mineiro, Querétaro and Fluminense before retiring in 2015.

Ronaldinho, meanwhile, has previously named former AC Milan defender Paolo Maldini as his toughest opponent; a sentiment also shared by fellow Brazilian forward Ronaldo Nazario.

Speaking to FourFourTwo, Ronaldinho said: "It has to be [Paolo] Maldini. Too many skills. It is impossible not to be amazed by how he made it all look effortless, especially when you get to play with him."

Ronaldinho would often shine against Real Madrid. Image credit: Getty

Ronaldo also told Italian outlet Il Messaggero: "Toughest defender I've faced in my career? Paolo Maldini would be the toughest ever. Among other Italian defenders, I would say [Fabio] Cannavaro, [Allesandro] Nesta and [Pietro] Vierchowod, all of which were very strong."