Babel, reminiscing back to when he played under Benitez at Anfield, wrote on Twitter: "Benitez on his way to Real? He will make Ronaldo a great defender…"
The tweet was retweeted over 3000 times inside the first hour, favourited over 1000 times, and drew a whole host of comments - particularly from disgruntled Liverpool fans, angry that the former Netherlands international had taken an unprovoked pop at Rafa.
Benitez is still a hugely popular figure in the eyes of the Liverpool supporters after guiding the club to their fifth European Cup 10 years ago.
That unforgettable evening in Istanbul - when Liverpool came from 3-0 down to eventually beat AC Milan on penalties - will always be remembered as one of the greatest nights in the Merseyside outfit's history.
Babel did little of note at Liverpool
While Babel might have been a cult hero for Liverpool fans for a few months - mainly on account of his social media exploits, rather than his achievements on the pitch - his legacy is likely to be left tarnished after this latest comment.
In truth, Babel did very little at Anfield, scoring 22 goals in 146 appearances for the Reds following his £14 million transfer from Ajax in the summer of 2007.
Babel blames Benitez
Five years later, after he had left the club, Babel pinned the blame on Benitez for his failure to become a Liverpool star.
“Rafa Benitez promised me a certain development, but very quickly he took away that promise and it was a totally different situation," the winger was quoted as saying by Goal.com. "I don’t think I ever really played more than three games in a row."
Benitez poised for toughest test
It's clear that Babel still feels a degree of bitterness towards Benitez, who has been chosen by Real Madrid president Florentino Perez to become the next manager at the Bernabeu.
It was announced earlier today that the Spaniard is leaving Napoli after two seasons with the Italian club.
And reports in Spain suggest Benitez could sell Ronaldo if the prolific superstar is unable to work alongside Gareth Bale, who is set to become the main man at the Bernabeu under the former Valencia manager.
Liverpool fans: how do you feel about Ryan Babel? Let us know by leaving a comment in the box below!