Mascherano began his career at legendary Argentine side River Plate in 2003, where his immense potential as a defensive midfielder quickly came to the fore.
After being linked with some of Europe's top sides, including Real Madrid and Deportivo de la Coruna, he eventually moved to Brazilian side Corinthians in 2005 for £7million.
Mascherano continued to impress at Corinthians, helping them to the Campeonato Brasileiro, together with Argentine team-mates Carlos Tévez and Sebastián Domínguez.
As one of the rising stars of the South American game, he established himself as Argentina's first-choice defensive midfielder at the World Cup in 2006, where he was widely regarded as one of their most influential players.
His performances brought him to the attention of clubs like Inter Milan and Manchester United, but on the final day of the 2006 summer transfer window, the shock announcement came that both Mascherano and Tevez had been signed by West Ham United for an undisclosed fee, in a move that was shrouded in secrecy.
Whilst the capture of Mascherano and Tevez was at first hailed by disbelieving Hammers fans, Mascherano struggled to settle at the East London club, making only limited appearances as the club floundered at the bottom of the division.
Mascherano expressed his desire to leave the club and Liverpool came to his rescue with a loan deal, after they bypassed FIFA Article 5.3, which states that a player may not play for more than two clubs in any one season (Mascherano had already played for Corinthians and West Ham).
FIFA approved the deal on January 31, 2007. However, the Premier League announced they wanted to 'take time to satisfy itself with the proposed arrangements'.
Something was odd about Mascherano's third party ownership during his time at West Ham United and in March 2007 the Premier League charged West Ham with breaking rule B13, concerning acting in good faith, and rule U18, which concerns the influence of third-party ownership. In April Hammers were handed a world-record fine of £5.5 million.
Mascherano subsequently joined Liverpool on a permanent 18 month deal worth £1.5million and made his debut against Sheffield United in February, hastily establishing himself as a starter at the club.
Mascherano ended his first year with a Champions League final against AC Milan and although voted Man of the Match by the fans, Liverpool lost 2-1.
The Argentinean made his move to Anfield permanent, ending his association with Media Sports Investments, in February 2008 for a fee of £18.6million.
During the 2007/08 season Mascherano hit the headlines when he was sent off against Manchester United at Old Trafford. After picking up a yellow card for a poorly timed tackle he was dismissed protesting to the referee and had to be pushed off the pitch by Steven Gerrard and Xabi Alonso.
The Football Association handed him a three match ban for improper conduct and a fine of £15,000.
