The Uruguayan international's move from Anfield to Spanish outfit Barcelona was confirmed yesterday afternoon, with a £75m fee believed to have been exchanged.
However, having relied heavily on the 27-year-old, Barton "can't believe Liverpool didn't fight harder to hold on to" a player that scored 31 goals in 33 Premier League outings last season.
"Some front two Barca have now with Messi and Suarez. Can't believe Liverpool didn't fight harder to hold on to him," Barton wrote on Twitter. "He's was arguably the form player in the world last season. How do you replace that? Big test for Rodgers and co."
Due to the ban that he received for biting Italy defender Giorgio Chiellini in the group stages of the World Cup, Suarez will not be permitted to make his debut for Barca until late October.