Young opener Prithvi Shaw underlined his class with a century against a quality Tamil Nadu attack to lead Mumbai to 314 for 7 on the opening day of the Ranji Trophy Group C match.
Electing to bat after winning the toss, Mumbai suffered an early setback when comeback man V Yo Mahesh got Akhil Herwadkar in his first over.
The opener was trapped leg-before for a duck.
Shaw and Shreyas Iyer, who has been picked in the India T20 team to face New Zealand, were in an aggressive frame of mind and attacked the Tamil Nadu bowlers.
In a quick start despite the loss of Herwadkar, the 50 came in the eighth over.
They raised the teams 100 in the 20th over as Iyer rattled along striking some beautiful shots in the process.
He raised his half-century at run-a-ball.
Shaw appeared subdued but played some splendid shots too as the Tamil Nadu bowlers struggled to contain the free-stroking Mumbai batsmen.
Iyer fell at 106 after a fluent knock of 57 which included seven fours and two sixers.
He edged a delivery from Vijay Shankar to keeper N Jagadeesan.
The Mumbai batsmen continued to look for runs and Surya Kumar Yadav added 63 runs with Shaw in just over 11 overs to keep the momentum.
Shaw, who was 76 at the lunch break, only required another 26 balls to reach his century and continued to push the Mumbai score along.
The young right-hander hit 17 fours and two sixes before falling for 123 to R Ashwin.
The country's premier off-spinner had previously got rid of the aggressive Siddesh Lad.
Mumbai skipper Aditya Tare scored an important half-century to further the team's cause and added 63 runs with the experienced Abhishek Nayar, before Vijay Shankar provided TN with the much-needed breakthrough.
The all-rounder provided another wicket for Tamil Nadu by sending back Vijay Gohil in the final over of the day as Mumbai finished at 314 for 7.
It was another hard day for Ashwin as he bowled 29 overs for 77 in picking up two wickets while Yo Mahesh also scalped two Mumbai batsmen.
Left-arm spinner Rahil S Shah went for 82 runs in his 25 overs while young all-rounder M S Washington Sundar bowled only four overs.
Brief scores (Day 1): Mumbai 314 for 7 in 89.1 overs (Prithvi Shaw 123, Shreyas Iyer 57, Aditya Tare 53, Vijay Shankar 3 for 37, R Ashwin 2 for 77) vs Tamil Nadu.
At Vizianagaram: Andhra Pradesh 278 for 2 in 89.5 overs (G Hanuma Vihari 143 batting, D B Prashanth Kumar 127) vs Odisha.
At Agartala: Tripura 88 for 6 in 40 overs (B B Ghosh 42 batting, Ishwar Pandey 3 for 20) vs Madhya Pradesh.