Boss Jim Magilton admitted his side gave away "stupid goals†as the Blues fell to their third home league defeat of the season against Cardiff City.
Magilton said he was hoping his side could put a run together after Wednesday's victory over Bristol City: "We were trying to build up a head of steam but it just didn't happen for us. We started brightly and had one or two good opportunities and they threw bodies on the line.
"But they didn't have to work too hard for their goals - we can't afford to give stupid goals away like that.
"I thought we would create more opportunities but we petered out and didn't have the same intensity as the other night. And with 10 men it was going to be even more difficult.
"We never really put any passes together and our only real bit of quality was Jon's goal. In the second half, we pressed but their keeper never had a save to make and that was very disappointing.
"We tried to stay positive with a 4-3-2 formation, hoping to exploit Danny Haynes's pace."
Magilton thought Ben Thatcher's first yellow card was unwarranted but had no complaints regarding the second: "I haven't spoken to the referee but I thought he got a bit of the ball for the first tackle. The second one was a bit silly."
Thatcher took a similar view: "I'm gutted. I got something on the ball for the first booking and thought that was harsh.
"The second one, we lost possession and their player has come inside me and I've caught him. I couldn't have any complaints over that one and having already been booked, the referee had no option."
Thatcher will now miss one game, while Owen Garvan is also out of next week's trip to Coventry having reached five bookings. Alex Bruce has served the first game of a four-match ban.
Cardiff boss Dave Jones had praise for striker Jay Bothroyd after the game: "Jay's quick and strong and has a great touch for a big fellow.
"If he could head the ball a bit better he could be the complete centre-forward.
"Now he's got to keep it going because, with the quality I've got at my disposal here, he knows it would be an easy option for me to leave him out.
"Eight clubs is a lot to have had and at every other one he's started well and then drifted. I think the penny's dropped for him now.
"He's spoken to me about getting his head right and working hard and that's the challenge for him from now on. All I can do is give him a stage to perform on.
"In the first half we deserved to be in front because we played some super football. Then we took our foot off the gas, taking an extra touch and giving a sloppy goal away.
"In the second half we had to do it all again and we certainly would have made life a lot easier for ourselves if we'd scored a third goal."