At his peak, Tristan was considered amongst the best strikers in Europe, displaying a vast array of skills and off-the-ball movements. The striker was best known for his time with Deportivo de La Coruna.

​

Tristan came through the Real Betis B youth side before finishing his sporting development with the reserves of Mallorca. He made the top flight in 1999-2000 with Real Mallorca finishing the season with 18 goals from 39 matches. After nearly joining league Real Madrid during the summer of 2000, a deal which was barred by the out going president. The strker found himself joining Galician club Deportivo de La Coruna. In four seasons he played 177 games produced 87 goals, leaving the club in July 2006, amidst accusations he did not live like a professional athlete, and not doing all he’s capable to reach his best level.

​

After being linked with several clubs in Spain and overseas Tristan agreed to rejoin Real Mallorca after a six-year hiatus but was released in January 2007, due to lack of fitness, form and no goals after 13 games.

​

He signed a one-year contract with Serie A side AS Livorno Calcio in July 2007, but Tristan ultimately failed to impress with the Tuscany team, scoring only once in 21 outings in a season which saw them eventually drop to the Second Division.

​

On 30 September 2008, it was confirmed he was undergoing a trail with the Hammers and on the 14 October the Spanish striker became the first new recruit under Gianfranco Zola. The 32-year-old, capped 15 times by his country, had been without a club and was a free agent since leaving Livorno at the end of the previous season.

​

After being given time to work on his fitness, his first taste of the Premiership coming from the substitute’s bench against London rivals Tottenham Hotspur on 8 December 2008 in a 0-2 reverse at Upton Park. With Hammers first choice striker Dean Ashton out for most of the season, Diego along with David Di Michele were both given their chance at Upton Park. But sadly they failed to impress and were both were released on 30 June 2009.

​

On 24 July 2009, the journeyman returned to his native Andalusia after 14 years to join second division club Cadiz. In his only season, his 29 appearances and 8 goals were not enough as his team was relegated after finishing off in 19th position.