A no-holds-barred clash is on the cards between the two former champions as the reward for victory would be a direct spot in the T20 tournament's final at the Eden Gardens on May 24.
It's not a knock-out for the losers too as they will get a second chance to enter the summit clash by taking on the winners of the May 20 Eliminator at Pune between Rajasthan Royals and Royal Challengers Bangalore in the Second Qualifier at Ranchi on May 22.
Two-time winners Super Kings will have to forge a new opening combination in the high-pressure game following the departure of McCullum to play in the Test series against England commencing on May 21.
The New Zealander, who piloted his country into the World Cup finals recently, has been the top-order fulcrum along with West Indian Dwayne Smith (325 runs) with a tally of 436 runs - his side's highest - under his belt with his belligerent stroke-play.
Veteran Australian batsman, Michael Hussey had opened with McCullum at Mohali, without both tasting success, in the Super Kings' one-sided victory.
Now the under-cooked Hussey, with the experience of that six-ball single against his name, is expected to launch the innings with West Indian Smith against the potent MI new ball attack of Lasith Malinga and Mitchell McClenaghan.
Malinga and left-armer McClenaghan -- easily the find of the season for MI with his swing, pace and bounce -- have forged a deadly combination, grabbing 19 and 14 wickets respectively.
Luckily for MI, McClenaghan is still available to play as he is part of New Zealand's ODI squad against England.
With Hussey yet to find his feet, pressure would be on Smith, South African Faf du Plessis, Suresh Raina and captain Mahendra Singh Dhoni to give the push against a varied and incisive MI attack in which the experienced Harbhajan Singh and the impressive Jagadeesha Suchith are to bowl the middle overs.
MI's batting, in contrast, has taken on a well-established look and would be difficult to stop once it gets going on a track that generally encourages aggressive stroke-play.