Who speaks at a news conference ahead of the first leg at Stamford Bridge , Di Matteo .
Who has revived Chelsea 's fortunes after taking over from Andre Villas - Boas , said playing Barca represented the biggest challenge a manager could face .
Speaking at a news conference ahead of the first leg at Stamford Bridge , Di Matteo , who has revived Chelsea 's fortunes after taking over from Andre Villas - Boas , said playing Barca represented the biggest challenge a manager could face .