After two defeats and a faded match in Lucknow, CSK came back to winning ways as MS Dhoni and co. secured second place in the table while a fifth defeat of the season for Mumbai meant they remained stuck in the middle of the table.
Chahar, in his second match after returning from injury, wreaked havoc with the new ball as he partnered with Tushar Deshpande reduced Mumbai to 14 for three in the first three overs of the match. But as Nehal Wadhera’s first IPL fifty (64) gave the visitors some respite in the middle overs, Pathirana’s superb display of deadly bowling restricted Mumbai to 139 for 8.
In the under-par chase, Conway (40) and Gaikwad (30) once again shone on top, while Shivam Dube (26*) and Ajinkya Rahane (21) also added big points as Chennai finished the pursuit with 14 spare balls.
Earlier, Rohit Sharma had a questionable record as the MI skipper was out for a record 16 ducks, the most by a batsman in IPL history, in the Mumbai fight at 139.
Batted, Mumbai changed his batting order to help Rohit come out of his poor running. The skipper had failed to reach double figures in his last three innings.
Ishan Kishan (7) and Cameron Green (6) led off the innings, but both fell cheaply.
Tushar Deshpande bowled Green for six, while Kishan skied Deepak Chahar (2-18) and was out.
Rohit, making at number three, then went down to back point for a three-ball duck as Mumbai were down to 14-3 in 2.5 overs.
Nehal then played the saving hand with his maiden IPL half-century off 46 balls. He put on 55 off 46 balls with Suryakumar Yadav (26), before Ravindra Jadeja bowled the latter in 11th.
Wadhera hit 64 from 51, hitting eight fours and a six, and struck up a further 54 from 42 off Tristan Stubbs (20), as Mumbai reached 123-5 in 17.3 overs.
But the final push for fast runs never came as the Chennai bowlers scored three more wickets in the space of seven deliveries.
Pathirana finished with 3-15 in four over bowling at the death.
In reply, Chennai got off to another strong start with openers Conway and Gaikwad posting 46 for 25.
Veteran spinner Piyush Chawla (2-25) continued his fine form for Mumbai by picking up another pair of wickets. First he caught Gaikwad, before trapping Ajinkya Rahane lbw for 21.
Conway, however, held on even as other batters hit. Impact player Ambati Rayudu scored 12, before Shivam Dube helped finish things off quickly with 26 not out from 18 balls.
Dube hit three sixes as Chennai beat Mumbai at home for the first time since 2010 and moved up to second place in the points standings.
(With inputs from AP)