<p>In April 2011, Barcelona and Real Madrid faced each other four times in just 18 days: twice in Champions League semi-finals, once in La Liga, again in the Copa del Rey. Those 18 days descended into a strained, feverish period that de ned an era for one of football's most intense rivalries.<br><br>Barcelona was Guardiola's past and his present. Born and raised in Catalonia, he had grown up at the club, eventually witnessing the footballing phil...