After finishing second in the Premier League last term to book their place in European football's showpiece event, Spurs are expected to push on and challenge for a place in the latter stages, but Gallas is not sure whether they have what it takes to do so.
"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 is quoted as saying 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."
Gallas spent three years at White Hart Lane in his playing days and also represented London rivals Chelsea and Arsenal.