Spurs have been dumped from the FA Cup and now are struggling to stay in the top four.
"I think we have to improve a lot," Gallas said. "Even if we have good players and a good squad this result shows we are not ready yet."
Asked if he was worried that the season was falling apart, Gallas added: "Yes, everybody is worried because at the beginning of the season everybody was talking about us, saying we play good football, we can finish third, we are 10 points in front of Arsenal.
"Now we are five points behind them and we have lost the semi-final. It will be difficult because Chelsea and Newcastle are behind us and, after that victory, Chelsea will be very strong. I think they will finish very well so we have to finish well as well."