In the end, Mumbai Indians ended up edging the final by just one run, but they made it a lot tougher for themselves by missing several opportunities to dismiss the one batsman who stood between them and victory. Shane Watson was the beneficiary of as many as four missed chances before he was finally run-out for 80. Mumbai Indians were lucky that those misses didn't cost them the title.
It started in the third over, when this happened:
Malinga to Watson, 1 run, a direct hit at the bowler's end from point and Watson would've been walking back! This was a gentle bunt, waste of a run, loaded with so much risk. Ishan Kishan the fielder. Lucky break for Chennai Super Kings again
According to ESPNcricinfo's Luck Index, which calculates and assigns a value to every luck event in a match, that run-out chance cost Mumbai 25 runs, which means Super Kings would have scored 25 fewer runs had Kishan hit the stumps then (though Kishan did compensate later, with a superb direct hit to dismiss MS Dhoni at a key stage of the match). Then, from the ninth to the 16th overs, Watson was reprieved thrice more, as Malinga and Rahul Chahar (twice) dropped catches of varying degrees of difficulty.
The chance in the 14th over was worth more than the one in the ninth because of how many runs Watson went on to score in the balls he faced after the event. When he was dropped in the ninth over, Watson was on 31 off 26, and scored 49 off 33 after that (strike rate 148); in the 14th over, he was on 42 off 40, and scored 38 off the remaining 19 balls he faced (strike rate 200).
The luck impact for each of these events is calculated by estimating how many runs the other batsmen may have scored off the balls that Watson faced after the event. For the ninth-over drop, Luck Index calculated that the remaining Super Kings batsmen would have scored 16 fewer runs than Watson did in those 33 extra balls he faced; for the 14th-over drop, the calculation was that the others would have scored 19 fewer runs. Importantly, between the two chances, he only scored 11 off 14 balls, which is why the impact of the latter event is greater.
In the 2018 tournament too, Watson was the recipient of a huge slice of luck in the game against Rajasthan Royals, when he was dropped in the first over, while on eight, and went on to score 106. On that occasion, his innings took Super Kings to victory; this time, Mumbai were good enough to steal a win.