|Full name||Koikili Lertxundi del Campo|
|Date of birth||23 December 1980|
|Place of birth||Otxandio, Spain|
|Height||1.68 m (5 ft 6 in)|
|Playing position||Left back|
|* Senior club appearances and goals counted for the domestic league only and correct as of 8 June 2014.
† Appearances (Goals).
Playing fourth division football just two seasons before moving to Athletic Bilbao, Koikili was signed from third level team Sestao River Club for the start of 2007–08. He made his La Liga debut on 26 August, playing the full 90 minutes in a 0–0 home draw against Navarrese neighbours CA Osasuna, whose B-side he had already represented in the late 90s/early 2000s.
For much of the season's duration Koikili was first-choice, dislodging international Asier del Horno. On his 27th birthday he scored his first top level goal, in a 1–1 home draw against Real Murcia.
Koi appeared slightly less in the following two seasons for Athletic, but still contributed with 52 official games combined (ten in the Spanish Cup, with the team reaching the final in the 2008–09 edition, and one in the newly created UEFA Europa League). On 11 January 2009 he netted the 1–1 at Atlético Madrid, as the Basque eventually won it 3–2.
Koikili was deemed surplus to requirements at Athletic in 2011–12 after the appointment of manager Marcelo Bielsa, alongside teammates Aitor Ocio and Iban Zubiaurre – he remained with the team however. On 25 June 2014 he retired at age 33, after spending two seasons at CD Mirandés.
- "Koikili, de la lucha grecorromana al Athletic de Bilbao" [Koikili, from freestyle wrestling to Athletic Bilbao] (in Spanish). El País. 21 August 2007. Retrieved 7 July 2012.
- "Athletic Bilbao 0–0 Osasuna". ESPN Soccernet. 26 August 2007. Retrieved 7 July 2012.
- "Athletic Bilbao 1–1 Murcia". ESPN Soccernet. 23 December 2007. Retrieved 7 July 2012.
- "Atlético Madrid 2–3 Athletic Bilbao". ESPN Soccernet. 11 January 2009. Retrieved 7 July 2012.
- "Koi, entre los ocho leones descartados por el argentino" [Koi, amongst eight Lions deemed surplus to requirements by Argentine] (in Spanish). El Mundo Deportivo. 14 July 2011. Retrieved 7 July 2012.
- "Koikili Lertxundi, de 33 años, se retira del fútbol profesional" [Koikili Lertxundi, 33 years old, retires from professional football] (in Spanish). EFE. 25 June 2014. Retrieved 18 August 2014.
- "Only way to stop a genius". The Sunday Times. 26 April 2009. Retrieved 16 April 2013.