Bengal stunned heavyweights Karnataka by seven wickets with inspirational performances from pacer Mukesh Kumar and opener Abhimanyu Easwaran to storm into the Syed Mushtaq Ali quarter-finals here on Tuesday.
Karnataka, however, is still in contention having qualified as the second team from the group and will be among six second-placed teams fighting for the remaining three quarter-final places.
Mukesh (3/33) dismissed India Test opener Mayank Agarwal (4) and the talented Devdutt Padikkal (0) in a space three balls as Karanataka failed to recover from the early blows to be restricted for a modest 134/8 at the Nehru Stadium.
In reply, Bengal opener and former captain Easwaran returned to form with a stroke-filled 49-ball 51 not out to steer the win with two overs to spare.
Bengal, who made a group stage exit in the last edition, faced a must-win scenario after Mumbai hit the top gear in the final group B league thrashing Baroda by 82 runs to lift their run-rate to 0.990.
Indian Test vice-captain Ajinkya Rahane continued his sublime form to slam a fourth half-century in five matches (71 from 45 balls; 8x4, 2x6).
His opening partner Prithvi Shaw too was back among runs in a blistering 63-ball 83 (6x4, 4x6) as the duo fired all cylinders in an entertaining 153-run (100 balls) opening partnership to lift the total to 193/2.
In reply, Baroda were restricted to 111/9 with young off-spinner Tanush Kotian claiming 4/16.
But the resounding win came a tad too late as Bengal ticked all the boxes to top Group B with a better net run rate (0.995) than Karnataka (0.379) who still qualified finishing second after both the teams finished with 16 points.
Mumbai finished with 12 points with three wins and two losses.
"Mumbai won earlier today and to qualify we had to win this match. We were focused and determined to do well," skipper Sudip Chatterjee said.
"Our bowlers showed the way with Mukesh's two wickets in the first over as it put pressure on a strong Karnataka side. Shahbaz, Pradipta took wickets at crucial times to restrict the run flow. A very good display by the team led by the bowlers."
On Abhimanyu's return to form, he added, "It's always good to see Abhimanyu scoring well for Bengal, he's an asset to the team."
Bengal think-tank had recalled the former skipper Abhimanyu in their match against Services on Monday after they suffered a shocking 10-run loss to Mumbai.
The move paid dividends as Abhimanyu played the role of an anchor after skipper Chatterjee (4) fell cheaply in the first over.
Abhimanyu stitched two small partnerships with Writtick Chatterjee (18) and Wriddhiman Saha (27) in the middle before Kaif Ahmed (34 not out) lent him match-winning support.
Earlier, Karun Nair was the top-scorer for Karnataka with a run-a-ball 44 (5x4) as none of their batter failed to convert their starts with Bengal bowlers taking wicket at regular intervals.
Left-arm spinner Pradipta Pramanik took 2/33, while Shahbaz Ahmad (1/15) and Akash Deep (1/19) were at their tidy best to restrict the run flow. Mukesh was also brilliant on the field and ran out BR Sharath.
Brief Scores
Karnataka 134/8; 20 overs (Karun Nair 44, Mukesh Kumar 3/33, Pradipta Pramanik 2/33) lost to Bengal 138/3; 18 overs (Abhimanyu Easwaran 51 not out, Kaif Ahmed 34 not out) by seven wickets.
Mumbai 193/2; 20 overs (Prithvi Shaw 83, Ajinkya Rahane 71) beat Baroda 111/9; 20 overs (Tanush Kotian 4/16, Mohit Avasthi 2/23) by 82 runs.
Chhattisgarh 176/3; 20 (Shashank Chandrakar 67, Sanjeet Desai 62 not out, Amandeep Khare 35 not out) beat Services 141; 19.5 overs (Rahul Singh 64; Shubham Agarwal 5/13, Ravi Kiran 2/35) by 35 runs.