Career
Osasuna Born in Pamplona, Navarre, Merino began his career with Civil Defense Amigó, and later moved to California Osasuna. He made his senior debuts with the reserves in the 2013-2014 season, in Tercera División. On 31 January 2015, Merino was definitely promoted to the main squad, being awarded the number 8 jersey.
He was a regular starter in his first year, helping them narrowly avoid relegation.
Borussia Dortmund On 15 February 2016, Merino signed a four-and-a-half-year deal with Borussia Dortmund, which was made effective on 1 July.