Frank Lampard admitted Ross Barkley had been "naive" after the Chelsea midfielder was pictured on a night out in Liverpool.
But the Blues boss insisted Barkley had not "committed a crime" by being out on the town on Sunday night.
Photos of Barkley appearing to argue with a taxi driver, having apparently spilt chips in the back of a cab, were published in newspapers ahead of the Blues' Champions League trip to Lille.
Lampard said he had spoken to Barkley, who has travelled with the squad to France, about the incident and revealed the 25-year-old England international admitted he had made a mistake.
Lampard said: "In terms of permission, I don't expect people to ask permission to be in Liverpool on their day off. That's not a problem. Especially with his family there. As an issue, he hasn't broken the club code about being out.
"In the modern world, Liverpool is the least of my worries. It is only a few hours to get up there and back. Especially when your family is up there. It is important for people to see them.
"To address the issue, first and foremost, he hasn't broken a club code. The lads were given a day off on Sunday.
"He hasn't committed a crime - other than eating chips in the back of a cab which is probably a bit out of order for the cabbie!
"But on a serious note, what he has done from my point of view is be naive to be out on that evening in the build up to a Champions League game.
"He has admitted that as well. I am very aware of that. On a professional level, those are little things that shouldn't happen.
"From my point of view, as well, I like Ross. I have had absolutely no problem with him since he has been here.
"He works hard and wants to do well for this club. This morning he admitted to making a mistake. I will take that one at face value and we move on."
The chips are down in France for Chelsea, who need to take something from the crucial Group H clash following their defeat by Valencia.
Lampard will check on the fitness of midfielder N'Golo Kante, who has been out with an ankle injury.
"He has trained this morning. He got through training okay. He is one we still have to assess in the morning. So we are positive that he will be fit to play," added Lampard.
"Everyone is working towards getting him regularly fit so he can play some continuous games. I am hoping that is coming really soon because obviously we need him."
Lille lost 3-0 to Ajax in their opening group match, but defender Cesar Azpilicueta is not taking them lightly.
"Lille may have less experience than us but they are at home," said Azpilicueta.
"They have great supporters, the team will obviously rely on the supporters to put a lot of pressure on us. There will be a lot of pressure. This is a special competition.
"Lille have been fighting hard to get into this competition. They have a lot of talent. They move well, pass and create opportunities. Also they have experienced players like Loic Remy, who I have played with before.
"But regardless we are here to take three points home."