The former New Zealand captain laid the foundation while Karthik smashed 48 off 26 balls which was largely responsible in Lions crossing 175-run mark.
The Tamil Nadu wicket-keeper-batsman struck two fours and as many sixes in his breezy knock after McCullum hammered the MI bowlers all round the park, striking six boundaries and three towering sixes.
It was an off day for Sri Lankan pacer Lasith Malinga, who replaced Kiwi Tim Southee. Malinga went for 51 in his four overs --- his most expensive spell in the tournament.
Put into bat, Gujarat Lions, had a disastrous start losing opener Dwanye Smith for a duck. He gave an easy catch to Nitish Rana at backward point off Mitchell McClenaghan off the very second ball.
Malinga, conceded 12 runs in his first over at the Wankhede track, where the ball came on to the bat.
Skipper Suresh Raina and McCullum then conjured an 80 run stand off 64 balls, with McCullum being the more aggressive of the two.
The Kiwi, made his intentions clear as he first hit Jasprit Bumrah coming down the track and then smashed two sixes off Malinga, one over point and other over mid-wicket, in the sixth over, as the visitors made 46 before the fielding restrictions were lifted.
Malinga conceded 27 runs in his first two overs. McCullum kept on hammering the bad balls, be it Krunal Pandya or seasoned Harbhajan Singh.
Raina and McCullum, who rotated the strike well, completed their 50 run stand in 42 balls.
At the half way mark, Gujarat Lions were 75/1. As the two were looking good, Harbhajan (1/22 in 4 overs) stuck in the 12th over removing Raina (28 off 29 balls), who was caught by MI skipper Rohit Sharma as the visitors lost their second wicket on 81. Harbhajan once again was economical in his four-over spell.
McCullum, who regained form in the last math, was going strong before Malinga cleaned him up on 64, with the scoreboard reading 3-99 in the 14th over.
Bumrah, who was hit for three fours, gave away 19 runs in the 17th over.
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