The 40-year-old Dhoni handed the captaincy to Jadeja this season and it has been a scrappy start for Chennai, the tournament's other powerhouse, who have only won two out of their seven games and are second last in the 10 team league.
Chennai had a dream start and dismissed both Mumbai openers, Rohit and wicketkeeper Ishan Kishan, on zero in the very first over rookie left-arm pacer Mukesh Choudhary.
Mukesh bowled tight, menacing lines but was not aided by the unusually sloppy Chennai fielders. He bowled three overs and took three wickets, including explosive South African teenager, Dewald Brevis (4), for 19 runs.
Mumbai innings was stabilised by Suryakumar Yadav, who hit an impressive 32 off 21 balls, and two rookies in the middle-order, Tilak Varma, who remained unbeaten on 51 off 43 balls with three fours and two sixes, and Hrithik Shokeen, who fell for 25.
Varma held the Mumbai innings and was helped by lower-order cameos by West Indian Kieron Pollard (14) and Jaydev Unadkat, unbeaten on 19 off 9 balls.
New Zealand's Mitchell Santner bowled three tight overs for 16 and took one wickets. West Indian veteran Dwayne Bravo took 2-36 in his four overs and Sri Lankan Maheesh Theekshana took one wicket in his four overs for 35 runs.
Chennai had a bad start and lost their in-form opener Ruturaj Gaikwad on the first ball of their innings for a duck.
Australian left-arm pacer Daniel Sams took Gaikwad's wicket, one of four in his four over spell where he gave away only 30 runs.
Sams took key Chennai middle-order wickets -- Mitchell Santner (11), Ambati Rayudu, after his promising 40 off 35 balls with two fours and three sixes, and in-form Shivam Dube (13) -- to make a match of Mumbai's below-par target of 156 to win.
The leader of Mumbai and India pace-battery Jasprit Bumrah went wicketless in his four overs for 29 runs.
The other Chennai opener Robin Uthappa (30) fell to Unadkat, who also took South African Dwaine Pretorius' after he hit crucial 22 off 14 balls.
Unadkat gave away 48 runs in his four over spell and bowled the all important last over of the Chennai chase and was hit all over the park by vintage Dhoni.
The cash-rich tournament has been expanded to 10 teams and 74 matches but league games would be restricted to four venues in Mumbai and Pune.