Tshimanga, the top goalscorer in the National League, needed oxygen and was stretchered off late on in the second-half.
The tackle, which Town coach Danny Webb said was ‘reckless’ and should have resulted in a red card, went unpunished by referee Greg Rollason.
To compound the Spireites’ misery, Terras substitute Ahkeem Rose equalised eight minutes into 12 of added on time to cancel out Alex Whittle’s second-half opener.
Oldfield said: "He (Mnoga) is distressed.
"He is distraught.
"I want to take this opportunity to put on record that there is no way he meant to hurt Kabongo.
"I know Kabby from when he was a young player at Milton Keynes. He is a great player and he has done fantastically well over his career but this season in particular.
"There is no chance that Haji meant to hurt him.
"I have not seen the tackle back. From my point of view, when Kabby received the ball in some space, I was a bit annoyed and I just turned my back and did not see clearly what happened.
"We are devastated for the player and for Chesterfield but there was certainly no intent from us
"We certainly need to do all we can for Chesterfield’s player.”
The struggling Terras, who are third from bottom, fell behind when Whittle struck the opener in off the post on 70 minutes for his second goal of the season.
Chesterfield, who were far from their best and were particularly poor in possession, had some good chances early on and paid the price at the end.
Oldfield added: “It was a really difficult game, I thought the boys showed character to come back from a goal down.
"After last week we needed to show something today and the boys certainly did, they worked really hard and managed to get something out of the game.
"I thought it was a good, little team move. There was some quality in the counter and the passes and I thought the boys worked it well.
"It was very nice to see in terms of trying to get something which I think the boys deserved.