City, playing in their blue shirts - we've won all our games when we've played in red so far this campaign, were three down after 46 mins and left themselves a mountain to climb.
It could have been worse, other results weren't too bad. Huddersfield were the big movers climbing to third place after beating Wolves.
Leicester go top on goal difference after a late equaliser at Birmingham.
Cardiff conceded two goals in two minutes in the first half from Andy Reid and Daniel Ayala. Billy Sharp scored the third a minute into the second half.
City's line up with Helguson up front on his own was too cautious and it was only when Mackay made substitutions bringing on Noone, Gestede and later on Mason that City started to press the home side.
Helguson scored to make it 3 - 1 with 16 mins to go but despite losing Adlene Guedioura to a red card 7 mins from the end, Forest held on. Lee Camp making several saves to earn Forest the points.
So another disappointing away game to rank down there with the trips to Bristol City and Palace.
This coming week City play twice at home. So the red shirts are back and hopefully the victories.