Rayudu, promoted to No 5 ahead of Kieron Pollard, justified the faith in striking a quick-fire unbeaten 53 in 27 balls, laced with 3 sixes and four boundaries as it helped MI to recover from 120 for four after 15 overs.
Rayudu put on 61 runs in 30 balls with West Indian Pollard, who made 24 in 14 balls before departing with MI finish the innings with a flourish.
Captain Rohit Sharma too promised much before departing on 27 before Rayudu and Pollard combined forces to provide MI with a good total at the packed Wankhede Stadium.
Watson kept shuffling his bowlers and reaped rewards. Dhawal Kulkarni snapped up the wickets of Patel and Rohit while giving away 26 runs in 3 overs while the other three wickets were shared by Tim Southee, Juan Theron and Ankit Sharma.
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The diminutive wicketkeeper-batsman struck Dhawal Kulkarni for two fours off successive balls in the medium pacer's first over.
Later Patel got couple of more boundaries in one over from Juan Theron, playing his first IPL game of the season, to keep up a healthy run-rate.
However, the Gujarat-born batsman departed again after getting a good start in the fourth over when Kulkarni exacted revenge by catching him off his own bowling off the 17th ball he faced in which Patel struck five fours.
Simmons, at the other end, held his end up after being dropped off the second ball of the innings when he edged Southee to Royals stumper Sanju Samson who grassed the ball off his gloves. The West Indian too departed in the tenth over when set after raising MI hopes by pulling Watson for a four and a step-out six in successive balls in the previous over.
He failed to connect a sweep shot off left arm spinner Ankit Sharma and declared out leg before. His knock was laced with one six and four fours.