Hansen believes Chelsea must target the makeshift defender tomorrow night.
"He is a midfielder playing at centre-half and he is only 5ft 8ins, but Barcelona are such a good team that he has managed to get away with it until now.
"When he was at Liverpool, Mascherano was always impulsive and he liked to hunt in a pack when he chasing the ball. That remains the case, but you cannot play like that as a centre-half.
"As a result, Mascherano couldn’t adjust his feet quickly enough to get himself back into position.
"He almost gifted Chelsea an opening goal from their first throw-in last week when he failed to deal with Branislav Ivanovic and his presence will not help the Barcelona back four build a sense of assurance."