MS Dhoni was the final-over hero as Chennai Super Kings kept Mumbai Indians waiting for a first Indian Premier League win with a dramatic three-wicket victory.

CSK needed 17 off the last over from Jaydev Unadkat in the battle of the bottom two to win only their second match and Dhoni delivered, hitting the four he needed off the last ball to leave the Indians shellshocked.

Mukesh Choudhary (3-19) dismissed Rohit Sharma and Ishan Kishan for first-over ducks after Mumbai were put in by Ravindra Jadeja at a raucous DY Patil Stadium on Thursday, but they recovered to 155-7.

Teenager Tilak Varma top scored with 51 not out off 43 balls, while Suryakumar Yadav (32) and debutant Hrithik Shokeen (25) also chipped in.

CSK dropped four catches, including Varma being given a life by Dwayne Bravo when he had scored only two, in a sloppy display in the field following such a great start.

All-rounder Bravo took 2-36 before Unadkat added a brisk unbeaten 19 and Daniel Sams dismissed Ruturaj Gaikwad with the first ball of the run chase.

Sams (4-30) also saw the back of Mitchell Santner, Shivam Dube and Ambati Rayudu, with Mumbai favourites when Chennai were 106-6 in the 16th over following Jadeja's departure for only three.

Dwaine Pretorius made 22 and the ice-cool Dhoni stepped up when CSK needed him, making 28 not out off 13 balls to leave the Indians rooted to the bottom of the table after losing all seven games.

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Choudhary gives CSK dream start

Left-arm seamer Choudhary rocked Mumbai by removing both openers in the first over, with Rohit taken by Santner at mid-on off the second ball and Kishan losing his off stump.

Dewald Brevis became Choudhary's third victim off the final ball of the third over, reducing the Indians to 32-3.

CSK's fielding did not match the standard of their early bowling, captain Jadeja guilty of two of their dropped catches as they let Mumbai off the hook to an extent.

Dhoni still leading by example

He may have handed the captaincy over to Jadeja, but Dhoni showed he will always be a leader as he steered the holders home.

They needed 28 off two overs and 16 from deliveries after Unadkat trapped Pretorius leg before. 

Step forward the 40-year-old Dhoni, who clattered the left-armer for a straight six and struck the next ball for four, then scampered through for two before dispatching the last delivery into the leg side for a match-winning boundary.