Ole Gunnar Solskjaer felt Cardiff City took additional motivation from Stoke City being awarded a penalty in Saturday's 1-1 draw.
Referee Howard Webb chose to point to the spot late in the first half when Peter Odemwingie, making his return to former club Cardiff, went down under a clumsy challenge from Kim Bo-kyung.
Marko Arnautovic fired Stoke ahead from 12 yards, but the hosts secured a point courtesy of a penalty of their own in the 51st minute, scored by Peter Whittingham.
Solskjaer believed Kim was unfortunate to be penalised for his challenge on Odemwingie, but said his players were "galvanised" by the setback.
"I still feel what I felt at the time - that it's not a penalty - but I accept Howard has to make a decision there and then," said the Norwegian.
"He hasn't got an advantage of all the replays we have but, for us, of course it galvanised everyone in the dressing room - we felt hard done by.
"I didn't have to say a lot at half-time apart from maybe try to control your emotions because that's important when you get decisions like that against you.
"They (Cardiff's players) felt hard done by. They were there very close to it and they said let's just make sure we use this to gain some momentum and get some energy."
Stoke boss Mark Hughes, meanwhile, was disappointed with the decision to award Cardiff a penalty, and felt it handed Solskjaer's men a burst of momentum.
"The neutrals in the ground would probably have thought they were a couple of soft penalties. I'm not going to surprise you by saying I thought ours was a valid penalty and rightly given," said Hughes.
"My view on Cardiff's penalty is that it was very soft and the lad has actually looked for a movement from Steven N'Zonzi that would allow him to go down and I think he was always looking to go down in that situation.
"He drew the movement from Steven - (it was) very minimal, if any, contact and obviously difficult for (referee) Howard Webb when players go down in those situations. It's difficult to read whether it's a correct decision or not.
"That just came at a time in the game that was a little bit frenetic for us. It was probably the only time in the game where Cardiff got a little bit of momentum and created a few opportunities for themselves."