Liverpool manager Brendan Rodgers has warned Raheem Sterling about the lifestyle he expects him to lead after the striker was apparently filmed taking nitrous oxide.
Rodgers stressed that he felt Sterling was "super-professional" but he would need to speak to the 20-year-old about the latest reports concerning his off-field behaviour.
Footage of Sterling apparently inhaling the substance, known as "laughing gas" and described as a legal high, was published on a newspaper's website during Liverpool's 2-0 defeat of Newcastle at Anfield on Monday.
Sterling impressed on the field, scoring the opening goal, but Rodgers was immediately asked about The Sun's report after the game.
Rodgers said: "For me it is something that when you are professional sportsperson at the top level of the game, I don't think it is something you should be doing. It is as simple as that.
"But I will speak to him on it, to see what he says on it. As you can imagine, I have only seen this today.
"We want players here who are super-professional and focused on their football. I know he is. He very much is focused on his football and improving as a player.
"As I have said before, young players make mistakes. As long as they learn from them, that is what is important."
The matter adds to the controversy currently surrounding Sterling amid a wrangle over a new contract. Sterling risked the wrath of supporters a fortnight ago by admitting he had rejected a £100,000-per-week deal in an interview that was not sanctioned by the club recently.
Another newspaper also published pictures of him allegedly smoking a shisha pipe over the weekend.
Rodgers stressed that any repercussions following the latest matter would be dealt with internally. He added that he did not feel the matter was a distraction.
He said: "You see the way he plays. He is a kid that is very strong-willed and strong-minded. He should have had a hat-trick, his performance was outstanding.
"I will speak to Raheem. Until then, it is something we will deal with internally."
Former Liverpool defender Jamie Carragher believes Sterling has been guilty of naivety on occasion over the last year, with regard to his publicised problems away from the field, but added that the youngster can treat the experience as a learning curve.
"Whether you're a Premier League footballer or you're a 20-year-old kid or whatever, you make mistakes at that age. I did and I'm sure we all do," Carragher said on Sky Sports.
"It's just important he learns from it because Raheem Sterling, for how good a footballer he is, needs to be on the back pages, not on the front pages and that's a problem for him in these last few months.
"But he's a young player, he made a few mistakes and hopefully in years to come he learns from them."