In reply to Vidarbha's mammoth 499, Bengal, resuming day three at 89 for three, were bundled out for 207 in the second session to concede a 292-run first-innings lead.
After enforcing follow-on, Vidarbha pacer Lalit Yadav ripped apart the Bengal top-order, picking up the wickets of Abhishek Raman and Koushik Ghosh in three deliveries.
At stumps, the home team was struggling at 86 for three in their second essay. Sudip Chatterjee was unbeaten on 40 with skipper Manoj Tiwary on 36 following a 76-run unbroken partnership.
Earlier, Tiwary, resuming on 36 in the first innings, could not make it big and was cleaned up by Rajneesh Gurbani in the 39th over to end his overnight partnership with Ghosh on 89.
Gurbani (2/43) made another breakthrough in the first session in the form of Wriddhiman Saha, who got out for zero after consuming 39 deliveries, as the Bengal innings wobbled after the departure of the two experienced players.
Batting at a snail's pace, Ghosh took 138 balls to bring up his fifty, and got out at the same score after facing seven more deliveries.
Akshay Wakhare added two more -- Shreevats Goswami (9) and Aamir Gani (11) -- to take his tally to three wickets and it was a matter of time before Bengal's first innings folded in 81 overs with Aditya Sarwate dismissing Ashok Dinda and Ishan Porel in five balls.
"We will have to bat till tea in the second innings and we will try our best to secure a draw," skipper Tiwary said after the days' play.
A loss for third-placed Bengal, who are on 13 points after three matches, would deal a big blow to their knockout hopes.
In Kalyani: Vidarbha 499
Bengal 207; 81 overs (Koushik Ghosh 50, Manoj Tiwary 50; Akshay Wakhare 3/45, Lalit Yadav 2/43, Rajneesh Gurbani 2/43, Aditya Sarwate 2/27) and f/o 86/3; 29 overs (Sudeep Chatterjee 40 batting, Manoj Tiwary 36 batting; Yadav 3/16).
In Dharamsala: Himachal Pradesh 175 and 167; 49.5 overs (Nikhil Gangta 41; Shahnawaz Hussain 6/53).
Chhattisgarh 456; 135.2 overs (Rishabh Tiwari 131, Amandeep Khare 78, Manoj Singh 67, Ashutosh Singh 54; Rishi Dhawan 3/127, Sidharth Sharma 3/100).
In Delhi: Services 263 and 108/3; 34 overs (Ravi Chauhan 41 batting).
Goa 270; 117.5 overs (Keenan Vaz 70, Amogh Desai 52, Sagun Kamat 50; Sachidanand Pandey 5/61).
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