Mikel Balenziaga grew up in the Basque city of Zumarraga and attended Real Sociedad’s youth academy. After playing for the reserve team for two seasons he left to join Athletic Club in 2008. He was supposed to feature for Bilbao Athletic but beat out competition to earn a regular spot in the starting lineup for the senior squad, making his debut on 14 September, 2008 in a scoreless draw against Malaga. The following year he was loaned out to Numancia before joining Real Valladolid on a permanent move in 2011. Two years later Balenziaga was one of the most vital players at Real Valladolid and made his return to Athletic where he has since held the role as the team’s starting left-back.
Mikel Balenziaga is under contract through 2021 and his deal does not contain a release clause.