Spurs have kept just one clean sheet in the Barclays Premier League all season and dropped to fifth in the table after Saturday's setback.
Tottenham's defensive woes worsened when Bassong limped off with a hamstring strain and is now expected to be sidelined for five weeks.
But he still believes there is enough quality in Harry Redknapp`s squad to challenge for a place in the top four.
"We have big quality in the squad and if we improve and work hard we can take a top four position," said Bassong.
"We need to keep working and work every day because that game on Saturday showed you can never stop at that level. If you don't work, you are going to be disappointed again and again. To be in the top four, we need more."