Yves Bissouma will miss the start of the season after being suspended by Tottenham.
The midfielder apologised after posting a video of himself inhaling nitrous oxide on social media.
The Mali international uploaded clips of himself using the Class C drug - known as 'hippy crack' - onto Snapchat last weekend.
Bissouma could be seen laughing between taking hits of the balloon in footage he shared to his fans.
The incident came just hours after Spurs' final pre-season clash, where they lost 3-2 to Bayern Munich in the Visit Malta Cup.
Spurs boss Ange Postecoglou revealed that he has been suspended by the club for their Premier League opener against Leicester on Monday.
Postecoglou said: "Been in the game for a long time, when a situation like this arises, I've tried to look at them in a couple of ways. First there's a person and it's Biss and he's made a poor decision.
"There are still sanctions involved, and some of those are educational. He is a footballer with responsibilities.
"He won't be available on Monday. We've suspended him from Monday's game.
"He needs to build that trust back with both me and the group. The door is open for him and we can help him realise the decisions he makes impact the group."
Bissouma himself issued a statement apologising shortly after the video was picked up.
He said: "I want to apologise for these videos. This was a severe lack of judgement
"I understand how serious this is and the health risks involved.
"And I also take my responsibility as a footballer and role model very seriously."
As part of the Government's anti-social behaviour action plan last November, nitrous oxide was made a Class C drug under the Misuse of Drugs act.
This means that possession of the so-called 'laughing gas' with the intent to get high illegal.
Repeat offenders could face a two-year jail sentence, along with an unlimited fine.
Dangers of inhaling nitrous oxide can lead to nerve damage, depression, brain disorders and hallucinations as well as memory loss.
The incident is a major blow to Spurs ahead of their Premier League season opener away at Leicester.
Bissouma has starred in pre-season for the north Londoners, where he scored a superb solo effort in the 2-0 win over QPR at Loftus Road.
The ex-Brighton man rediscovered his form under Ange Postecoglou last season, where he proved to be a key player - making 28 top-flight appearances.