The next delivery was pulled over square leg for a six.
Kings XI kept their playoffs chances alive by beating Kolkata Knight Riders, but need to win their two remaining games and need other results to go their way.
Mumbai were left needing 16 from the final over and there was controversy after the first ball as Pollard was called for one short as he looked to keep the strike, with suggestions that he had done so deliberately. It (pitch) was a bowlers' graveyard.
Simmons, who scored his half-century off only 27 balls, hit five boundaries and four sixes, before a brilliant effort at the long-on boundary from Martin Guptill saw the Caribbean global head back to the dug-out.
Maxwell (1-8) applied further pressure on Mumbai as he conceded just eight runs in the two overs and also had Simmons caught splendidly by Guptill at long on. All this while, he had tried several variations to no avail, but hope did not desert him and neither did the yorkers, which he executed brilliantly and managed to keep Pollard at arm's length. Kings XI pacers Sandeep Sharma (1/42) and Mohit Sharma (2/57) were on the job, bowling two tight overs to take Kings over the line.
The giant Trinidadian complimented rival stumper Wriddhiman Saha, who notched up 93 not out in 55 balls, and visiting team skipper Glen Maxwell (47 in 21 balls) for powering KXIP to the tall score, only the third time they have reached 230 in ten editions of IPL.More news: More from Build: Microsoft unveils cross-device vision for Windows 10
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Test specialist Saha displayed another aspect of his batting when he hit a flurry of boundaries and sixes in his whirlwind innings.
Glenn Maxwell smashed his way to 47 runs in just 21 balls and laid the flawless platform for the middle order to go for broke. But in his last five innings, teams have bowled just three short balls to him.
MI bowlers had an off day as the visiting batsmen toyed with their bowling.
Mitchell McClenaghan ( 1-54), Lasith Malinga (0-45), Harbhajan Singh (0-45), Jasprit Bumrah (1-24), Karn Sharma (1 -32 ) and Hardik Pandya (0-29) were hammered to all parts of the ground. Interestingly, the bookies were nabbed from the hotel, where the teams - Gujarat Lions and Delhi Daredevils - were staying for their IPL match, held in the Uttar Pradesh city on Wednesday.
Punjab were well-poised at 173/2 at the end of 15 overs and smashed 57 off last five overs to post the their overall highest score at the Wankhede.
This time though, fortune was on Saha's side as he blasted 93 not out off just 55 balls to set up KXIP's total of 230/3. Karn Sharma played a cameo of 19 runs in six balls.