Defender Taylor Moore could not hide his disappointment after the narrow 1-0 defeat to Forest Green Rovers in Sky Bet League Two.
Rovers front man Christian Doidge scored the only of the game and Moore conceded the Robins had not been good enough on the day.
"To come away with anything less than a win from a derby is massively frustrating,” he said.
"Right from the start we were too deep and maybe gave them a bit too much respect when they had the ball.
The goal comes from that on second phase. It's a fantastic finish, but as a back four we have got to be doing a lot better.
"There was a lot to play for and we know the fans are hurting. The biggest part of our disappointment is the feeling we let the fans down.
"We didn't give up until the end and we tried to make it difficult for Forest Green, but with the quality we have in this team we should be doing better in these big games.
"The fans were fantastic, from start to finish they sang and it is hugely disappointing to not give them something to smile about.”
Moore admitted the Robins now needed to try and make amends in the remaining three league games.
"We have three games left and we need to produce three performances we can be proud of as we look to next season,” he said.
"We need to put in performances, especially at home when we play Coventry because we want the fans to come back next season.
"We've got to go in Monday morning and assess what went wrong this week.
"As staff and players, we need to sit down and talk about what went wrong and how we can correct those in the next three games we have got coming up.”