Steve Rhodes said it was the "right thing to do" for Worcestershire batsman Alex Gidman to retire hurt after being struck on the helmet by a bouncer from Nottinghamshire paceman Ben Hilfenhaus.
Gidman suffered concussion after receiving the blow shortly after lunch and he left the field during the following over from Samit Patel after a hard run three.
He did not continue his innings and after his withdrawal Worcestershire lost six wickets for 67 runs in being bowled out for 283 – a lead of 43.
Director of Cricket Rhodes told BBC Hereford-Worcester's Dave Bradley: “We think Alex (Gidman) is suffering from some concussion, so he's been off the field and feeling a bit drowsy and a little bit sick.
“One minute he's white and the next he's got a bit of colour.
"It was a bit of a blow around the temple area and we don't want any of our players in any danger.
"So, the right thing to do was to take him away from the heat of the match and give him some time off. We'll know how he is a little bit more tomorrow.
"He didn't go to hospital. The medical team didn't feel that was necessary and we do trust our medical team.
"Alex is fine, he is smiling and he is okay. It's just every now and then he feels a little bit sick. Obviously a little bit of concussion type symptons.
“It's been a tough day for him because he looked in great nick (13 not out with three fours) when he was out there.
“Then he came off, Joe Clarke's got given out and all of a sudden everything completely changed.
"These sort of things happen. You don't want momentum changes, but sometimes you can't do anything about that. But sad for us it did change the momentum of the game so now we're having to fight again."
Rhodes praised the innings of 99 from opener Richard Oliver.
He said: “It was a good knock from Richard (Oliver) and had he got that one more run it would have been, something like, his third century in 17 games.
"That sort of century ratio per games is excellent. If you have that in your career, you have done very well so people forget that a little bit.
"We are very pleased that he managed to practically get a hundred and he fought really well, played some good shots and hopefully confidence-wise that is going to do him the world of good."
Rhodes added: "There is still a bit in the pitch. It's a lot flatter now which you'd expect as the green tinges go from the wicket.
"It's probably a good cricket wicket at the moment and we look forward to some more good cricket in this game.
"Every hour is important, probably none more so than the first hour, but we will be looking to do our very best, try and skittle them out and chase the runs."
Nottinghamshire also have fitness problems with Luke Fletcher (hamstring) unable to bowl, Andy Carter (side) far from fully fit and batsman James Taylor picking up a hamstring injury.
Nottinghamshire Director of Cricket Mick Newell said; “It was a great effort from Andy Carter to bowl. He looks like an Egyptian Mummy under his shirt – he's got that much strapping.
“He was bowling at about 70 per cent, but the fact that he bowled is terrific.
"In fact I thought we showed real fight, throughout the side. We even pulled in our overseas player Dan Christian to field as our 12th man. He was meant to be playing golf, but little things like that show that people do care.
“Whatever happens in the game, we have got two injured bowlers and a batsman (James Taylor) who has injured his hamstring. So we have got eight fit bodies.
“We have given a lot in this game and we have got to keep on fighting because we have got to try and win the game.”