Known to his many fans as "El Mago", or "the magician", the Argentinean fullback come fly-half has dazzled opponents the world over with his pace and arsenal of kicking skills.

Hernandez made his debut for the Pumas in a 144-0 thrashing of Paraguay in 2003, but really came to prominence following his switch from Deportiva Francesca to Stade Francais. From fullback Hernandez became a force in the Top 14 and Heineken Cup, a devastating attacker joining the line and a solid defensive presence, always immaculate under the high ball. He is well remembered for a crunching, try-saving tackle on Leicester's giant Samoan wing Alesana Tuilagi in the Heineken Cup clash at Welford Road in 2006.

His real arrival on the world stage was signalled by his surprise selection at outside-half in the opening game of the 2007 World Cup, against hosts France. Despite being described in certain quarters at the world's best fullback, Hernandez had designs on the remainder of his career being spent in the outside half berth of both club and country.

Pumas' coach Marcello Loffereda's faith in Hernandez was rewarded by a breathtaking display of attacking skill as his side unceremoniously took the scalp of the hosts on their home turf. Hernandez continued at No. 10 for the remainder of the tournament, notching a hat trick of drop goals against Ireland in the pool decider and another against Scotland in the quarter-finals. The Argentinean effort ended in the semi-final at the hands of eventual champions South Africa, but Hernandez had impressed enough to be nominated for the IRB Player of the Year award for 2007.

A lack of opportunities in the No.10 shirt of Stade Francais led to rumours that Hernandez may be making the jump to England. However, such talk proved unfounded and Hernandez recovered from injury to rejoin Stade's tilt at the Top 14 and Heineken Cup in the 2008-9 season.

In the summer of 2009 he completed a switch to the Sharks in South Africa on a one-year deal with the Durban-based side, but his stay was cut short by injury and he was unable to play a Super 14 game for his new employers. After a lengthy lay-off, Hernandez confirmed in May 2010 that he would be returning to France that summer after agreeing a deal with Racing Metro.

He made his debut for his new club as a replacement in a win over Toulon and, after another cameo appearance against Clermont, was granted his first start, at fly-half, against Castres a fortnight later. However, the following weekend Hernandez picked up a thigh injury in Racing's clash with La Rochelle, raising more fears that injury might ultimately curtail his glittering career.

A knee injury sustained in March 2011 against Bourgoin put Hernandez out for the rest of the season. In August 2011 Hernandez and Argentina's worst fears were confirmed when the fullback was ruled out of the forthcoming World Cup.