Placed comfortably at 140 for two in 14.1 overs, hosts lost wickets in a heap as Mike Hussey's 56 off 33 balls and last match's hero Lendl Simmons' 25-ball-35 were the only significant contributions.
Hussey's innings was laced with two sixes and seven fours as he put on 87 for the opening wicket in 8 overs with Simmons but the home team failed to take full advantage of their electrifying start.
Skipper Rohit Sharma made 30 with four fours in 21 balls but his fall to an ill-advised cut shot that triggered a collapse.
Mumbai started in a blazing fashion thanks to Hussey's aggression after they were put in to bat by rival captain Kevin Pietersen. Hussey, with just one 50-plus score as his best effort this season, tore into the rival bowling attack with pulls and bottom handed shots before he was run out.
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The retired Australian left hander raced to 41 off just 20 balls in the first power play period of six overs and it contained seven fours and a straight lofted six off left arm slow bowler Shabaz Nadeem and his all-out attack helped Mumbai pile on 65 for no loss during this productive phase.
Hussey fell for 56 for the second time in the season, run out by a throw from point to wicket-keeper Dinesh Karthik, who whipped out the bails just in time to catch the retired Australian short of crease to leave MI at 120 for 2 with eight overs in hand.