Arsenal boss Arsene Wenger says Jack Wilshere is "not a smoker" after a picture emerged on social media of the midfielder holding a shisha pipe.
Wenger said Wilshere had apologised, but added: "One second of your life does not define who you are.
"He is not a smoker. He is sorry about what happened but he has to master his own life."
On Thursday, Wilshere, currently out of action with an ankle injury, posted a video of him in training on social media.
The England international wrote: "Worry about your character not your reputation, because your character is who you are and your reputation is only what people who don't know you think about you."
At Friday's news conference ahead of Saturday's north London derby against Tottenham, Wenger said: "This photo has been taken at half past 12 after the Super Bowl. I don't know what happened really. Away from the club, it is his responsibility to master his life.
"Today, everywhere you go people make photos, but one second of your life does not define who you are."
On the January transfer window
The Gunners signed defender Gabriel Paulista for £11.2m from Villarreal, although the Brazilian is unlikely to feature on Saturday. In addition to Gabriel's signing, the contracts of Chuba Akpom and Francis Coquelin were extended.
Wenger said: "I'm very happy with the business we did. We met our targets and extended Chuba Akpom's and Francis Coquelin's contracts. Gabriel is physically ready to play but is not used to our back four and hasn't mastered the language yet."
On Alexis Sanchez missing the north London derby
The Chilean forward has yet to recover from a hamstring problem.
"It's not easy to tell him he's not playing. He wants to play - he's so keen, but we have enough offensive power. We don't need to worry about being short on that front."