The MS Dhoni-led side has already reached the cut-off limit of 16 points as they roared back to form after two losses. They defeated Sunrisers Hyderabad on Tuesday night regain the top slot.
While CSK's must have welcomed Watson's return to form, the team would be hoping for Suresh Raina, Ambati Rayudu and Kedar Jadhav to get going ahead of the knockout phase.
The bowlers have played a big role in CSK's success so far, especially at home, on sluggish tracks. The much-improved Deepak Chahar will be key in the matches to come with his intelligent bowling at the start and at the death.
On the other hand, Mumbai have had a roller coaster season so far and they now need to be at their best in the last lap of the preliminary phase. In Rohit Sharma, they have a shrewd captain who leads from the front, and a solid batting unit that includes Quinton de Kock, Kieron Pollard and the Pandya brothers -- Hardik & Krunal.
Jasprit Bumrah & Co. will be wary of CSK's batting with Watson having found his mojo again and the ever-reliable Dhoni.
The visitors, currently in the third spot with 12 points from 10 games, are coming off a defeat against Rajasthan Royals and will be keen to keep themselves in the hunt for the playoffs.
SQUADS:
Chennai Super Kings: MS Dhoni (captain & WK), Suresh Raina, Ambati Rayudu, Shane Watson, Faf du Plessis, Murali Vijay, Kedar Jadhav, Sam Billings, Ravindra Jadeja, Dhruv Shorey, Chaitanya Bishnoi, Rituraj Gaikwad, Dwayne Bravo, Karn Sharma, Imran Tahir, Harbhajan Singh, Mitchell Santner, Shardul Thakur, Mohit Sharma, K M Asif, Deepak Chahar, N Jagadeesan (wk), Scott Kuggeleijn.
Mumbai Indians: Rohit Sharma (C), Quinton de Kock (WK), Suryakumar Yadav, Yuvraj Singh, Kieron Pollard, Hardik Pandya, Krunal Pandya, Mitchell McClenaghan, Jason Behrendorff, Mayank Markande, Rahul Chahar, Jasprit Bumrah, Anmolpreet Singh, Siddhesh Lad, Ankul Roy, Evin Lewis, Pankaj Jaiswal, Ben Cutting, Ishan Kishan, Aditya Tare, Rasikh Salam, Barinder Sran, Jayant Yadav, Beuran Hendricks.