Derbyshire 270 (Critchley 81*, Pennington 4-44) and 112 for 6 (Pennington 3-25) trail Worcestershire 421 by 39 runs
Dillon Pennington produced his career-best performance with the ball as Worcestershire closed in on victory after enforcing the follow-on against Derbyshire on day three of the LV=Insurance County Championship match at New Road.
The paceman bowled a series of excellent spells from the New Road End and was rewarded with figures of 4 for 44 from 19.4 overs. Club captain Joe Leach, Ed Barnard and Alzarri Joseph all picked up two wickets as Derbyshire were bowled out for 270 - despite a fine unbeaten 81 from Matt Critchley - in reply to Worcestershire's first innings total of 421.
Leach asked the visitors to bat again 151 runs in arrears half an hour before tea and they ran into trouble with Pennington again shining with three wickets as they closed on 112 for 6.
Worcestershire's bowlers were backed up by some razor-sharp catching.
Derbyshire resumed in the morning on 91 for 3 and Pennington's excellent opening spell brought him the wicket of debutant Ben McDermott. The Australian T20I international drove hard at a delivery which he edged to Daryl Mitchell at second slip.
Madsen completed his half-century off 127 balls with seven fours but added only one more run before Barnard ended his innings with Mitchell holding onto his second catch of the day.
Fynn Hudson-Prentice gave Critchley good support during a sixth wicket stand of 56 in 14 overs. But Leach ended the resistance of Hudson-Prentice on 25 when he mistimed his drive and was caught by Jack Haynes at third slip.
Critchley completed a 67-ball half century soon after the resumption when he pulled Leach for his eighth boundary.
Pennington came back into the attack and his first delivery saw Alex Hughes caught behind for 25. Joseph trapped Ben Aitchison lbw via a low full toss and then bowled Sam Conners as he backed away to leg.
Pennington wrapped up the innings when Dustin Melton was pouched by Fell at first slip - and he was back amongst the wickets when Derbyshire followed on.
Cox pulled off a superb one-handed catch low to his right after Pennington found the edge of Brooke Guest's bat on 7.
Leus du Plooy needed 30 balls to get off the mark before collecting two boundaries in an over from Joseph. But he picked up a key wicket when Derbyshire captain Billy Godleman edged another catch - this one head high - to Mitchell.
Spin was introduced via Brett D'Oliveira and he enjoyed a success with Du Plooy using his feet but only succeeding in providing a low return catch.
Pennington's sixth wicket of the match came when McDermott looked to work the ball to leg but went leg before. He was then indebted to a spectacular catch by Fell at first slip to dismiss Critchley.
It became 93 for 6 when Hudson-Prentice went back to D'Oliveira and chopped onto his stumps