Nottingham Forest manager Martin O'Neill believes his side paid the penalty for not being able to take the chances they created when they were in the ascendancy.
A header from Michael Ihiekwe won the game for Rotherham United who beat The Reds 2-1 and the Forest boss was left frustrated.
Speaking after the game, O'Neill said: "We didn't defend the set pieces in both halves and paid the penalty.
"There is no point in defending two or three set pieces half decently if you don't continue in that vein for the rest of the time. One in each half has cost us the three points.
"There were a couple of chances that we missed early on then they scored the goal, but we fought back and got the equaliser and then their goalkeeper makes a decent save from Lewis Grabban and then a few minutes later we concede the goal, so it was tough to take today."
The Reds did have positive spells throughout the contest but O'Neill stressed the importance of making it count when his side are on top.
He added: "We tried to get a little bit of width from our full backs and in that sense we played a diamond shape and I thought that there were periods in the game where we looked in control; whatever you say about it, once you are in the ascendancy you have to try and make it count.
"We had two great chances and we squirmed those and eventually we paid the penalty.
"There are small margins, but it is disappointing to lose all three points in the game and I am disappointed, the players are obviously and naturally the crowd will be."