Uefa is sending Italian refereeing great Pierluigi Collina to monitor Belgian match official Frank de Bleeckere's handling of a potentially volatile Champions League semi-finals clash between Barcelona and Real Madrid.
Uefa has named Collina, its head of referees, as its official observer at the Camp Nou tonight.
While Uefa sends a referee observer to every match it organizes, it is rare for Collina to be called in.
Uefa's choice of the 44-year-old de Bleeckere, who has a long-standing reputation as one of Europe's best referees, also reflects the high-risk status it has given the rematch of storied Spanish rivals.
After Barcelona won a bad-tempered first leg 2-0 last Wednesday, Madrid made a failed protest to Uefa about German referee Wolfgang Stark sending off Pepe when the game was scoreless.
Madrid coach Jose Mourinho was sent from the dugout by Stark for his comments about Pepe's red card, then later accused Uefa and its referees of actively helping Barcelona reach Champions League finals.
Mourinho included de Bleeckere in the supposed conspiracy after his handling of the second leg of last year's semifinal when the Portuguese coach's 10-man Inter Milan side eliminated Barcelona.
Uefa named another Italian official, Sergio di Cesare, to serve as its match delegate on Tuesday.
Uefa's disciplinary panel will meet Friday to examine six charges arising from the first-leg match.
Mourinho, who is banned from the touchline Tuesday, faces further punishment for his comments during and after the match. Pepe also faces a longer ban for his red-card challenge, and Madrid has been charged for its fans throwing objects and invading the pitch.
Barcelona's substitute goalkeeper Jose Pinto has been charged over his part in a touchline brawl at halftime.
Collina was referee for the second leg when Madrid and Barcelona last met in the Champions League semifinals.
In 2002, the sides drew 1-1 at the Santiago Bernabeu stadium allowing Madrid to advance and win the title.
Collina also refereed the 2002 World Cup final, when Brazil beat Germany 2-0, and Manchester United's 2-1 victory over Bayern Munich in the 1999 Champions League final.
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