Bopara's career best haul jolts Derbyshire
Derbyshire 280 (Bopara 5-49) and 150 for 1 (Godleman 75) trail Essex 538 for 7 dec by 108 runs
Derbyshire dug in obdurately in the final session at Chelmsford to hold up Essex's charge for a third Specsavers County Championship win of the season.
The visitors were forced to follow-on, finishing 258 runs adrift of Essex's massive first-innings total with Ravi Bopara taking career-best bowling figures of 5 for 49 eclipse his 5 for 75 Surrey at Chelmsford a decade ago.
With rain forecast for much of the fourth day, the Division Two leaders may yet rue putting down three relatively comfortable chances during the day.
Essex had wrapped up the Derbyshire first innings with five wickets in 16 overs after lunch. But they struggled to trouble the Derbyshire batsmen in the evening session as their advantage was gently whittled down.
Essex had not had much good fortune in the morning session, either, though it would have been better had Jesse Ryder and Tom Westley clung on to relatively simple catches in the slips in three balls off the luckless Aaron Beard.
Hamish Rutherford was the recipient of Essex's fumbling. But he had added just seven more runs before Beard showed his elders how to catch by holding on at square leg to dismiss him for 49.
That gave Bopara his third wicket of the innings, the second coming when Wayne Madsen got an inside edge and was caught behind. James Foster snapped up a second catch at the wicket when Shiv Thakor edged Ryan ten Doeschate.
The carnage began straight after lunch as Derbyshire collapsed inside 65 minutes.
Neil Broom went second ball after the break when he misjudged a ball from Tom Westley and was bowled. Seven balls later Tom Poynter chased a wide one from Bopara and became Foster's third victim.
Matt Critchley gave Bopara his fifth wicket when he departed lbw before Jamie Porter uprooted Tom Taylor's middle stump with his sixth delivery with the new-ball.
Ben Cotton, at No. 11, took 18 off one Porter over before being the last man to go when caught by ten Doeschate in attempting to hit Beard over the top.
Jaik Mickleburgh at gully dropped Chesney Hughes in the first over of Derbyshire's second innings. However, Hughes was back in the pavilion 27 overs into the innings when he pulled back as Bopara came in to bowl. After a lengthy consultation with the physio the Anguillan went off feeling unwell.
His opening partner Billy Godleman was steadiness incarnate as he reached fifty with the first of three successive fours through the off side against Westley. It had taken him 106 balls. He then punished Beard with two boundaries in two balls, but the youngster had the last word when he bowled the Derbyshire captain off inside edge and boot for 75.