Herwadkar made 161 off 272 balls with the help of 25 boundaries and three sixes, while Shreyas Iyer scored 82 off 124 balls (8x4s, 2/6s) to hand Mumbai 366 runs overall lead with three wickets and one full days play remaining.
Siddesh Lad (41) was the not out batsman at the crease when stumps were drawn.
Manan Sharma was the pick of the bowlers for Delhi in Mumbai's second essay picking up four wickets for 89 runs.
Replying to Mumbai's paltry 156, Delhi to witnessed a batting slump but just somehow managed to overwhelm the opposition score before being bowled out for 166 in 54 overs.
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Veteran Virender Sehwag top-scored for Delhi with a fulent 49 before being run out.
Pacer Shardul Thakur scalped five wickets for Mumbai giving away 54 runs.
Brief Scores:
Mumbai: 156 and 376/7 in 119.4 overs (Aditya Tare 23, Akhil Herwadkar 52
no out; Pradeep Sangwan 1-16)
Delhi: 166 in 54 overs (Virender Sehwag 49, Shivam Sharma 30; Shardul Thakur 5-54).