River Plate / Valencia

Dilahirkan di Río Cuarto, Córdoba, Aimar began his ascent to stardom with Club Atlético River Plate, whose first team he joined for the 1997–98 season, after rejecting a place at medical school, and with whom he quickly established himself as one of the best young players in Argentina.

Valencia CF of Spain signed Aimar in January 2001, at a price of €24 million. The purchase proved justified as he helped lead the team to a first-place finish in La Liga in 2001–02 (with 33 games and four goals), as well as to a runners-up finish in the previous seasons's UEFA Champions League, being defeated by FC Bayern Munich; he also won the 2004 UEFA Cup, appearing in eight scoreless matches during the campaign – this included the final against Olympique de Marseille, where he replaced Francisco Rufete with 30 minutes to go.

On 12 April 2006 Aimar was hospitalized after being diagnosed with acute viral meningitis,[3] but made a quick recovery and returned to play for his team. During his career with the Che, he was also often troubled with injuries.[4][5][6]

Zaragoza

During the summer of 2006, Aimar joined fellow top flight club Real Zaragoza for €12 million.[7] He made his league debut on 27 August in a 2–3 away loss against Deportivo de La Coruña, and scored two goals in his first four matches.

The Aragonese side were relegated at the end of 2007–08, with the playmaker appearing in 22 games without scoring while also often hindered with injuries.[8] During that campaign, he teamed up with former Valencia teammate Roberto Ayala.

Benfica

On 17 July 2008, after a period of intense negotiations, Aimar signed a four-year contract with Portuguese side Benfica for a fee of €6.5 million.[9] After a difficult first half of the season, he managed to overcome his constant injuries and finished it in good shape.

In 2009–10 Aimar was in better physical conditions, and displayed a good offensive chemistry with countryman Javier Saviola, newly signed, as Benfica had the best offensive record of the competition, with the help of top scorer Óscar Cardozo, winning the club's 32nd championship, after a five-year wait. He played 46 games in the following season all competitions comprised and scored seven goals, but the Reds only conquered the domestic League Cup.

On 6 June 2013, after 179 official appearances and 17 goals, 33-year-old Aimar announced he was leaving Benfica, thanking the club for "five wonderful years".[10]

Johor Darul Takzim

On 7 Ogos 2013, Presiden Johor Darul Takzim F.C. Tunku Ismail Ibrahim , disahkan Aimar menandatangai kontrak dua tahun bersama Johor Darul Takzim.[11][12]

Aimar sahkan keluar dari kelabnya pada 21 April 2014, kerana masalah kecederaan yang dialami.[13]