Barcelona are set to lose one of the greatest talents in football history after Lionel Messi informed the club he wants to leave.

Messi intends to make use of a clause in his contract that enables him to depart on a free transfer following the 2019-20 season.

That option reportedly had to be activated by the end of May, but the six-time Ballon d'Or is said to believe the extension of the campaign into August means it is still valid.

With potentially the biggest transfer in history on the horizon, we look at how Barca and Messi got to this point.

January 9 – Barcelona lose their Supercopa de Espana semi-final against Atletico Madrid 3-2 in Saudi Arabia.

January 13 – Despite the club being top of LaLiga, Barca confirm the dismissal of Ernesto Valverde. Quique Setien is appointed as head coach on a two-and-a-half-year contract, with a supposed return for Blaugrana legend Xavi failing to come to fruition.

February 3 – In an interview with Catlaan publication Sport, sporting director Eric Abidal says the club had begun considering Valverde's future after the 0-0 draw with Real Madrid on December 18. He adds that he and his colleagues identified "many players weren't satisfied nor working hard and there was also an internal communication problem".

February 4 – Messi hits back at Abidal, calling on him to name individuals rather than tar every player with the same brush. Writing on Instagram and highlighting a section of Abidal's quotes, Messi says: "I honestly don't like to do these things, but I think everyone has to be responsible for their tasks and take care of their decisions. The players [are responsible for] what happens on the pitch and we are also the first to recognise when we are not playing well. Those responsible for the area of​​ sports management must also assume their responsibilities and especially for the decisions they make. Finally, I think that when talking about players we should give names, because if not we are all getting dirtied and feeding things that are said but aren't true." Furthermore, ESPN report Messi has been playing through a thigh problem for a number of weeks after the club failed to sign attacking reinforcements and let Carles Perez and Abel Ruiz leave after Luis Suarez was ruled out for four months.

March 1 – Barca suffer a disappointing 2-0 loss to Real Madrid in the second Clasico of the season at the Santiago Bernabeu, with Zinedine Zidane's side going top of LaLiga as a result. However, the Catalan giants still managed to take a two-point advantage into the coronavirus lockdown.

March 30 – With a return of football yet to come onto the horizon, Messi confirms the players agreed to a 70 per cent pay cut. However, he makes it clear he is unhappy about pressure put on them. He posts on Instagram: "Much has been written and said about the Barcelona team in regards to the salaries of the players during this state of emergency. We want to clarify that our will has always been to take a cut in the salary we receive, because we fully understand that this is an exceptional situation and we are always the first ones to help the club when asked. Therefore, it does not surprise us that from within the club there were those who tried to put us under pressure to do something we always knew we would do. The agreement has been delayed for a few days because we were looking for a formula to help the club and its workers during these difficult times."

June 28 – During a 2-2 draw against Celta Vigo, Messi is accused of ignoring instructions from assistant coach Eder Sarabia during a drinks break. Setien denies the reports of a rift in the dressing room at a news conference the following day.

July 16 – Barca suffer a shock 2-1 home defeat against Osasuna, handing Madrid the league title. Messi makes his dissatisfaction known, saying that they must improve quickly or risk Champions League elimination in their last-16 second leg against Napoli. In a post-match interview, he told Movistar: "People are losing patience after defeats to Roma and Liverpool in recent years. We need a break and forget about this if we want to fight for the Champions League. We need to change a lot, otherwise we will also lose against Napoli. I already said before that playing like this we won't be able to fight for the Champions League and you see, we could not even fight for the league. We need to be self-critical."

August 14 – While they managed to get past Napoli despite an unconvincing perfomance, Barcelona are thrashed 8-2 by Bayern Munich in the Champions League quarter-final. It is their heaviest defeat in European competition and the most goals they have conceded in a single game since 1946.

August 17 – Setien is sacked by the club and presidential elections are brought forward to March as the club signals its intention to rebuild. It is reported that the majority of the first team are put for sale.

August 18 – Sporting director Abidal is relieved of his duties a day after informing Setien his time with the club was up.

August 19 – Barca icon Ronald Koeman is appointed head coach on a two-year contract. He said of Messi upon being presented to the media: "He is a Barcelona player. He has another year [on his contract]. I don't know if I have to convince him to stay."

August 20 – Messi meets Koeman to discuss his future with the club. RAC1 reports Messi told the new coach he is 'more outside the club than inside' and he had little faith in president Josep Maria Bartomeu. Koeman is alleged to have said to Messi: "The privileges in this squad are over, you had to do everything for the team. I'm going to be inflexible; you must only be thinking about the team."

August 22 – Tensions increase as Argentine publication Clarin claims Messi is furious that details of his meeting with Koeman were leaked to the media.

August 24 – Messi's close friend Suarez is one of four players - the others being Arturo Vidal, Ivan Rakitic and Samuel Umtiti - supposedly told by Koeman they have no future at the club.

August 25 – Messi informs Barca he intends to leave the club, using a clause in his contract to exit on a free transfer, via burofax.