Liverpool are currently one point behind City, and have played a game more than their rivals.
Mascherano said: 'We have to win but we cannot lose our heads.
Mascherano: In action against Unirea Urziceni in the Europa League on Thursday
'We have to go therethinking about winning but we have to play a very good game from thebeginning.
'We are one point behind them and some teams are very close to us so it's important to get the three points.
The Argentine star believes City have improved under new manager Roberto Mancini, and Liverpool's tactics would need to be spot on when they travel to Manchester.
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'Obviously when you want to win you have to go forward but you have to be careful about the counter attack because they have some very good players so we have to be clever.
'I think from the arrival of Roberto Mancini has improved them a lot. They won a lot of games in a row, then they lost some points but at the end (of the season), it is positive for them so maybe they will be more organised, more clinical and more direct so we will see.'
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