Santander-born Marcano, a youth graduate of hometown's Racing de Santander, made his first appearance with the main squad in an away win over UD Almería on 30 September 2007, due to injuries in the Cantabrian side.

[8] He was first-choice for most of the first part of his first season; however, after consecutive poor performances, he fell out of favour, even losing his position in the defensive pecking order to 19-year-old Argentine Mateo Musacchio (originally signed for the B side).

[11] Benefitting from injuries to both Mario and Rafa, he was regularly used in both defensive positions as the Madrid outskirts team narrowly avoided relegation; he netted his only goal of the season on 24 October 2010, in a 3–0 home win over Sporting de Gijón.

[12] The following 20 February on Racing's visit to the Coliseum Alfonso Pérez, he was sent off for a foul on Giovani dos Santos from which Pablo Pinillos scored the only goal from the penalty spot with three minutes remaining.

in Greece, where he playing alongside several compatriots – including manager Ernesto Valverde – and was essential in the double conquest,[14] Marcano was sold by Villarreal to FC Rubin Kazan in the Russian Premier League, for about €5 million.

[15] On 14 July he made his debut in the Super Cup as a second-half substitute in a 2–0 victory over FC Zenit Saint Petersburg, with his team being captained by compatriot defender César Navas.

[16] He played 11 times in a run to the UEFA Europa League quarter-finals, and headed a goal in a 3–2 home win over Chelsea on 11 April though the English club advanced 5–4 on aggregate.

[19] On 21 April 2015, Marcano was sent off for a second yellow card as Porto lost 6–1 away to FC Bayern Munich in the quarter-finals of the UEFA Champions League, being eliminated from the tournament despite having won the first leg.

[27] During his spell at the Stadio Olimpico, Marcano appeared in only 13 competitive matches,[28] with Federico Fazio, Kostas Manolas and Juan Jesus playing more frequently in central defence.