The Blues broke the deadlock after 75 minutes, courtesy of a close range effort from Ivorian frontman Salomon Kalou.
However, at the time of the strike, Ramires was off the field recieving treatment for a foul committed on him by Oscar Cardozo.
By the time he returned to the action, the game had already restarted and it appears he was unaware that Di Matteo's men had taken the lead.
He had told reporters in the tunnel afterwards that he was thrilled with a 0-0 draw and that any win in London and his side were through to the last four.
Chelsea now go into the second-leg game at Stamford Bridge with an all important away goal, giving them the advantage over their opposition to progress to the next stage of the competition.
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