Second-placed Chennai Super Kings are second with 14 points from 11 games, while Kings XI Punjab are third with 12 points from 10 games.
Mumbai and Rajasthan have played 17 matches so far- while the MI has 10, RR have emerged winners in 7.
In Mumbai, they defeated Kolkata by 13 runs, defending a total of 181/6, before the side travelled to Bengal and condemned the hosts to a 102-run victory, riding on Ishan Kisdhan's 21-ball 62 blast.
Jasprit Bumrah struck early to dismiss D'Arcy Short (4) in the first over to jolt the Royals. But their out-of-form skipper Ajinkya Rahane will need to pull his socks up.
Buttler hit a six over long-on off Mayank Markande to guide Royals to 83/1 at the halfway mark. Meanwhile, Buttler reached his fifth consecutive fifty - and equalled the record for scoring most consecutive IPL fifties with Virender Sehwag who had achieved the feat back in 2012.
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Liverpool , meanwhile, have still not secured a place in the Champions League next season - despite reaching this year's final. Added Liverpool captain Jordan Henderson: "Not many people would say we would get to the Champions League final".
Four days later in Indore, Buttler hammered a 39-ball 51 against Kings XI Punjab.
Lewis batted smartly as he opened his arms only after building his innings steadily after being dropped at individual score of five.
His knock was studded with 9 fours and 5 sixes. Rohit Sharma-led Mumbai team has made a comeback in winning form after losing several matches at the beginning of VIVO IPL 2018.
With Yadav and Rohit Sharma departing in the space of two deliveries, Lewis took the back seat for a while, to rotate the strike with young Ishan Kishan, who survived the hat-trick delivery of Jofra Archer. Ben Stokes also had a good day with the ball and finished with 2/26 in four overs. Mumbai's opponent, Rajasthan will also come with high confidence. Lewis broke the shackles by lofting Gopal for consecutive sixes in the ninth over. Slower ball from Dhawal Kulkarni, the new bowler in, Yadav looking to flick it, sends the ball straight to Gowtham who fails to catch the ball, which was dipping on him. We just have to come out and play good cricket.
It was a ideal partnership as Rahane played a run-a-ball knock, Buttler dealt in with fours and sixes to get the things going.