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It is the Indian Premier League’s very own El Clásico. Mumbai Indians against Chennai Super Kings, the game which will launch this season on Saturday, is a clash between the league’s two giants. Between them, the two have won seven of the 12 IPLs, filling 13 of the 24 spots in the final. Against all-comers, you could scarcely put a cigarette paper between the two: Mumbai have won more titles, Chennai have reached more finals.
And yet, this symmetry has curiously collapsed in their head-to-head games. Since 2013, Mumbai have beaten Chennai 11 times while losing only six games. Last year, culminating in their one-run victory in the final, Mumbai won all four Clásicos.
Mumbai’s ascendancy is a window into how T20 games are won and lost. In T20, more than any other format of the game, sides can be of essentially equal strength and yet, through generating favourable match-ups and targeting their opponents's relative weaknesses, one team can have the edge on the field. So has been the case for Mumbai against Chennai.
As teams, Mumbai and Chennai have very different characters. Compared to other IPL sides, Mumbai have an unusual reliance on quick bowling, led by Jasprit Bumrah and Lasith Malinga, with their home venue relatively conducive to pace. Chennai’s approach with the ball has been almost the antithesis: they have embraced spin, regularly fielding three specialist spinners in tandem on the spin-friendly pitches at Chepauk. Chennai have been quick to recognise that dominating at home is the easiest way to reach the play-offs every season — as indeed they have done during all 10 of their campaigns.
Yet their potency at home has wilted in the face of one foe: the Mumbai Indians. Last year, Chennai won all six of their home games against other IPL sides. But they were defeated comfortably the two times Mumbai came to town, losing first by 46 runs and then by six wickets with nine balls remaining.
If there is a defining feature of Chennai’s cricket, it is their prioritisation of control. In T20, MS Dhoni has said, "You're trying to manage the chaos." But Mumbai's entire approach has been designed to wrestle control from Chennai, opening up tiny wounds with a surgeon's precision.
When they bat, Chennai like to begin relatively circumspectly, setting the game up for Dhoni and the middle order. Mumbai have embraced how, against such an approach, the risk-reward equation makes attacking with the new ball a smart option. In 2019, they took 10 Powerplay wickets in four games against Chennai, attacking with new-ball swing from Jason Behrendorff and Lasith Malinga when playing in Mumbai and then with spin when playing away.
Only one member of Chennai's normal top six — Suresh Raina (who is not playing this year) — is a left-hander. This has freed Mumbai to pack their attack with spinners who could turn the ball away from the bat.
Left-armer Krunal Pandya opened in the last three games against Chennai, getting openers Shane Watson and Faf du Plessis out once apiece. In the middle overs, Rahul Chahar bowled immaculate leg breaks: in four games against Chennai last season, he conceded just 4.28 an over. Revealingly, left-arm spinner Anukul Roy’s sole game for Mumbai last season was in Chennai, providing a third option turning the ball away from right-handers.
The use of off spinner Jayant Yadav, in his sole game against Chennai, is a microcosm of how much Mumbai value match-ups. Jayant was whisked into the attack as soon as Raina came in, and dismissed Raina with his third ball. But without other left-handers to bowl at, Jayant only bowled three overs. "It was the call that we had to make, knowing that they have quite a bit of right-handers in their squad," skipper Rohit Sharma said after the game.
As Mumbai recognise, generating favourable match-ups for spinners are a double advantage. It is not just that batsmen score slower when the ball turns away from them. It is also that, when two right-handers are batting together, spinners can be deployed in a way that protects the shortest boundary; when a left and right-hander are in tandem, one batsman will always have the shorter boundary on their leg side. This all suggests that Chennai could benefit from sometimes promoting left-handers Mitchell Santner, Ravi Jadeja or new signing Sam Curran up the order.
Mumbai’s attack has also been uniquely well-suited to neutering Chennai at the death. With Malinga and Jasprit Bumrah, Mumbai have had two of the best death bowlers — arguably the best two — in T20 history. Since 2013, Chennai have lost a wicket at the death every 12 balls against Mumbai, denying Dhoni and the rest of the middle order a chance to finish the job. Chennai’s batting approach has been predicated on Dhoni’s preternatural ability to judge run chases; more than any other IPL team, Mumbai’s attack has been designed to prevent a final flourish.
In the field, Chennai's approach has revolved around maintaining iron control in the middle overs. Mumbai have recognised how a sturdy Powerplay can counteract this approach. Since 2013, Mumbai have only averaged 44 runs per Powerplay against Chennai — but, crucially, they lose wickets one-quarter less frequently than any of CSK's other opponents. With only one wicket down in the Powerplay and batsmen, often Rohit himself, set, Mumbai can then bat more comfortably against Chennai’s spinners.
Just as with the ball, Mumbai have tailored their line-up to turn Chennai’s relative weaknesses into roadblocks to victory. So Mumbai have regularly promoted Krunal Pandya, for his prowess against spin, saving Hardik Pandya and Kieron Pollard to attack with impunity, liberated by Chennai lacking express pace. On a slow pitch, the two shared 39 in 22 balls — Pollard top-scored with 41* — to set up Mumbai’s match-winning 149 in the final last year.
Both particularly excel against Dwayne Bravo, Chennai's premier death bowler. Often pre-empting Bravo's slower balls, Pollard and Hardik have scored 185 runs from Bravo for only four times out in the IPL. Mumbai deploy Pollard and Hardik, two of the most ferocious six-hitters in the world, not where they will face the most balls but where their skills are most damaging to their specific opponents.
The contrast with when Dhoni bats against Mumbai is revealing. With Dhoni batting at the death, Chennai’s biggest batting asset has been deployed against Mumbai’s best bowlers — a match-up that bowling sides always want to engineer, for it protects their weakest bowlers. But Mumbai’s approach has emboldened their supreme batting assets, Pollard and Hardik, to bat against Chennai’s weak links.
And so Mumbai’s advantage over Chennai is not rooted in having better T20 cricketers so much as in deploying them more effectively against their specific opponents. Chennai, for all their consistent brilliance in the format, have been out-thought by Mumbai.