Jurgen Klopp said Sergio Aguero is one of the best players he ever managed against after the ex-Manchester City forward announced his retirement.

Aguero, who joined Barcelona from City earlier this year, confirmed his decision to retire on Wednesday at an event featuring president Joan Laporta and the Blaugrana's first-team players, while representatives of the 33-year-old's other clubs – including Pep Guardiola – also attended.

The Argentina international suffered chest pain in a LaLiga match against Deportivo Alaves on October 30, which Barca confirmed was down to a heart arrhythmia.

Further tests resulted in Aguero being ruled out for three months to undergo a "diagnostic and therapeutic process". After consultations with specialists, he was told it would be too great a risk to continue playing.

Aguero scored 260 goals in his 10 years at City, with 184 of these coming in the Premier League, making him the highest-scoring overseas player in the competition's history.

Having scored league goals at a rate of one every 108 minutes, the best frequency of any player to net at least 20 in the competition, Aguero could play another 2,520 minutes of Premier League action (the equivalent of 28 full games) without scoring and he would still have the best minutes-per-goal ratio of any player to have scored 20 times or more.

Aguero scored seven league goals against Liverpool, with his last such strike a thumping opener in a crucial 2-1 win in January 2019. City edged out the Reds by a single point in that season's title race.

Asked about Aguero's impact on the Premier League, Klopp – whose side face struggling Newcastle United on Thursday – told a news conference: "Massive, massive.

"I really feel for the boy. He obviously made a move to Barcelona not to retire but for another exciting move in his career, he was not able to contribute because of his issues and I really feel for him.

"He had a great career, there will be a moment where he will see that as well and see that 33 is an age where other players retire but for other reasons, but of course for him at the moment he is of course in shock, that's what you get when you have to announce something like this.

"The impact he had on the Premier League, on football, I think was incredible. The whole time at City, even before Pep arrived there, the goals he scored, the importance of the goals he scored.

"Since I'm here, when we played against City, even if he was not too busy scoring against us, he was massive. He scored a very important one I remember. I don't know him as a person but as a player I can say he's one of the best I ever faced."