Leeds United boss Neil Warnock admitted his side were second best in the 4-0 defeat at Manchester City.
But he says he felt aggrieved by the award of the spot-kick, given by referee Mark Clattenburg for the slightest tug on Aguero by United defender Tom Lees.
“I know Mark sees it differently and he’s had a good game today but he wouldn’t give a foul anywhere else on the pitch,” said Warnock.
“The lad is clever the way he appeals but it’s such a soft penalty.
“”And so we’re 2-0 down after 14 minutes. You think the worst but I think they’ve done really well.
“We have had great cup runs this season but I think in the first 10 minutes the young lads were a little bit overawed. But we hung in there and I was quite pleased they didn’t fold.
“The second goal is vital when they’re desperate to get a result but it’s never a penalty in a million years.
“Let’s be fair, they were still better than us but it made it easier for them.”