At stumps on the second day of the match, Mithun Manhas, (60) and Manan Sharma (13) were at the crease.
Gambhir top-scored for the visitors with 64.
Having bowled out Mumbai for 324 after the hosts resumed at overnight 252/6, Delhi trailed the defending champions by 133 runs in their first innings when stumps were drawn for the day.
While Sehwag was out caught behind for just nine off another out-of-favour India player, pacer Zaheer Khan, Gambhir struck 12 fours during his 147-ball knock at the Bandra Kurla Complex.
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Pacer Parvinder Awana was the star performer for Delhi with ball, returning impressive figures of five for 72 in 27 overs.
While he could get just one wicket, Mumbai captain Zaheer smashed an entertaining 50-ball 51 to prop up his side's innings. He hit four sixes and three fours during his brisk knock.
Brief scores:
Mumbai 1st innings: 324 all out in 112.2 overs (Siddhesh Lad 74, Wasim Jaffer 61, Aditya Tare 53, Zaheer 51; Parvinder Awana 5/72).
Delhi 1st innings: 191/3 in 56 overs (Gautam Gambhir 64, Mithun Manhas 60; javed Khan 2/36).