And Gallas, who reached the quarter-finals with Tottenham in 2010-11, says his former club lack the skill set required in Europe's premier club competition.
"It was a big shame what happened to them last season, but this Tottenham squad is a little too young for the Champions League," he said in quotes reported by The Daily Star.
"Against Monaco and Bayer Leverkusen in the group games, it showed that they needed more experience.
"The Champions League is different to the Premier League. You need experience, you need to be more clever and stay focused.
"If you compare our squad back then with now, we had many older and more experienced players."