Mark Yates was furious with Cheltenham's defending in the 2-1 defeat at Torquay as Guy Branston opened the scoring with a header from a Craig Stanley corner.
Branston`s second goal in successive games was followed up by a clinical six-yard finish from on-loan Ipswich teenager Ronan Murray, before Robins full-back Danny Andrew grabbed a late consolation with a free-kick.
Yates said: "It's disappointing we have been undone by a set-piece because that's what we practice defending against in training. We have got undone by a set-piece again and again we will have to work on it on the training ground.
"Apart from that in the first half, we felt comfortable. They didn't really do anything to us, apart from a couple of long-range shots.
"I know they are good on set-pieces and I have known for plenty of years that they have been good on set-pieces. We had a couple of good chances ourselves in the first half.
"In the second half, we didn't do enough. We made some bad decisions with the ball and some bad decisions without the ball. We just didn't do enough to get ourselves back into the game. We weren't as good as we were on Saturday and we have got to be right at it every game."