Worcestershire gained a first innings lead of 43 but lost six wickets for 76 runs after Alex Gidman retired hurt suffering from mild concussion on the second day of the LV = County Championship match at Trent Bridge.
The visitors struck back with the wickets of Michael Lumb, Brendan Taylor and Alex Hales in the Nottinghamshire second innings. They closed on 115-3 – a lead of 72.
Worcestershire were well placed at 204-3 shortly after lunch after opener Richard Oliver had extended his overnight 52 not out to 99 before being dismissed.
But then Gidman (13) was struck on the helmet by a bouncer from Ben Hilfenhaus and left the field during the following over from Samit Patel after running a three.
Tom Fell followed up his career best 142 against Middlesex at Uxbridge by making another 72 but wickets fell steadily at the other end after Gidman's enforced absence.
Joe Clarke (0) was trapped lbw by Hilfenhaus – although relays suggested some contact was made with bat on ball – and then Brett Hutton picked up three wickets in three overs.
Ben Cox (9) was bowled after not playing a shot, Ed Barnard (4) was adjudged lbw and Fell's innings ended when Chris Read took a fine diving catch.
Two boundaries from Joe Leach brought up the 250 in the 78th over but Hilfenhaus returned with the new ball to claim another lbw victim in Jack Shantry (9).
Yet another lbw accounted for Saeed Ajmal (7) from the bowling of Andy Carter who was able to bowl after his side injury yesterday although Luke Fletcher (hamstring) was ruled out.
Leach finished unbeaten on 24 with four boundaries as Worcestershire gained a first innings lead for the seventh time in nine LV = CC matches this season.
It had gone smoothly before lunch for Worcestershire as Oliver and Fell resumed the innings on 89-2.
Oliver added 71 in 24 overs with Fell for the third wicket.
The left hander hit 13 fours and a six in his 173 ball knock and was within one run of his third LV = CC ton when he was caught behind by Read off Patel.
Nottinghamshire started their second innings after tea and Charlie Morris made the first breakthrough when Lumb (12) perished to a fine catch by Clarke at mid wicket after clipping the ball off his pads.
The home side were only one run in front when Barnard trapped Brendan Taylor lbw for 32.
Hales hit Leach for successive boundaries but perished to the next delivery on 24, being caught by Charlie Morris at deep mid wicket with the total 69-3.
Shantry bowled a probing and accurate spell of nine overs for eight runs which might have brought him some tangible reward.
Ajmal came into the attack for the first time at 91-3 after 27 overs.
The catalogue of injuries in the game continued with Notts batsman James Taylor picking up what appeared to be a hamstring injury and needing a runner in Hales.
Taylor finished unbeaten on 20 and Riki Wessels 25 not out