 The younger brother of Athletic Bilbao, Real Madrid and Colorado Rapids player Aitor Karanka, he came up through the ranks of the Basque giants, and first appeared with the first team on 14 May 2000, playing 15 minutes in a 0–0 La Liga away draw against RCD Espanyol.After a loan stint to CF Extremadura in 2000–01, where he scored 13 second division goals, Karanka returned to Athletic, with virtually no impact (six games, although he scored once in a 3–2 thriller win at RC Celta de Vigo, as Bilbao trailed 0–2 with eight minutes remaining).He subsequently returned to the second level, helping Real Murcia achieve promotion in 2002–03 by netting 13 goals, and adding seven in next season's top flight as the club returned to where it came from.