Salah's sensational 2017-18 continued with a four-goal haul as Jurgen Klopp's side romped to a 5-0 success at Anfield on Saturday, the Egypt international taking his tally to 36 goals across all competitions this season.
Four years ago, Gracia's Osasuna were thumped 7-0 at Camp Nou by Barca with Messi scoring a hat-trick and the Spaniard said even the best-laid plans can be ripped to shreds by players like Salah and the Argentina superstar.
"Many times it is not so important what your plan is, no matter how hard you work on it, because a player like that can change it in an instant," he said.
"I remember that [7-0] game, you don't need to remind me! But I also remember I went there the next season and won!
"They are both incredible players - they were both unstoppable, yes. Honestly, both are fantastic, and now Salah is in a very good moment, one of the best in Europe.
"It is very difficult to play against them, because they can both score in any moment. That is the same with both, they have so many qualities, they can do it in a single moment.
"You can do everything right in your defence, and in one moment you are lost.
"You can have plans to stop them, you have to try and we did it [against Messi] with Malaga yes. But players are always the most important element in a game. Players like Messi and Salah, they make decisions, and they decide games. That is what happened with Salah.
"It is difficult for us stopping an individual like Salah like it is difficult stopping a team like Liverpool. Sometimes you just can't do anything.
"But not only Salah, the whole Liverpool team is one of the best teams in Europe right now. They have a high pressing level, higher level than Barcelona. But both teams are in this moment the best in Europe."