The Catalans will possibly be without their playmaker in Tuesday\'s crunch encounter versus the Rossoneri as the Spain international is being plagued by muscular problems.Barcelona coach Pep Guardiola has received some worrying news from the treatment table ahead of the second leg of their Champions League quarter-final against AC Milan as he will possibly have to make do without Xavi due to injury, El Mundo Deportivo reports.The influential midfielder featured for only 15 minutes in Barcelona\'s 2-0 Liga win over Athletic Bilbao on Saturday, and missed Sunday\'s training session due to a muscular problem.It is not yet exactly known how serious the 32-year-old\'s injury is, but the Spain international could miss Tuesday\'s encounter at Camp Nou due to the knock.Xavi is expected to undergo a number of tests during Monday\'s training session at 18.00CET to determine whether he will be able to feature versus Milan.Barcelona were held to a scoreless draw at San Siro last week, and will be looking to beat the Serie A champions on Tuesday in order to book their ticket for the semi-finals.