Marcos was born in
Santander,
Cantabria. Following an unsuccessful spell in
Real Madrid's academy, Marcos' reputation continued to grow at
Atlético Madrid, and he was at the time the country's most expensive signing when
FC Barcelona paid 150 million
pesetas for his services in 1982. In his
first year he scored six goals in 30 matches in the league, and also an
injury time header against Real Madrid in
that campaign's
Copa del Rey final, which ended with a 2–1 win. However, Marcos was also one of four
Barça players who failed to find the net in
the final of the
1985–86 European Cup against
FC Steaua București, in a
penalty shootout loss, as
goalkeeper Helmut Duckadam saved all taken attempts. He retired in 1991 after a return to Atlético Madrid, marred by a serious knee injury, and after helping his first club Racing to
return to the
Segunda División. Subsequently, Alonso became a coach. In his first experience he led lowly
Rayo Vallecano to a first-ever victory over Real Madrid at the
Santiago Bernabéu Stadium (2–1), managing Racing and
Sevilla FC afterwards (
one top-flight promotion with the latter followed by
immediate relegation). In the 2000s, Alonso was in charge of Atlético Madrid – second tier,
no promotion–
Real Zaragoza,
Real Valladolid,
Málaga CF and
Granada 74 CF. ==International career==