Frank Lampard believes injured Chelsea midfielder Ross Barkley showed "a lack of professionalism" after he was pictured shirtless in a nightclub during the international break.

The 25-year-old, who has been sidelined with an ankle injury, has been left in London while the Blues take on Valencia at the Mestalla Stadium in the Champions League on Wednesday night.

But Chelsea boss Lampard insisted Barkley remained in his plans and challenged the England midfielder to get fit and prove his worth on the pitch.

"There are two separate issues, one is the headlines this week, Ross knows how I felt about the first headline," said Lampard.

"I backed him then and I still back him now. But he showed a moment of a lack of professionalism as far as I'm concerned.

"It's not something that I want to be a pure dictator about and come down hard on, because I also understand all my players are humans and have lives.

"I don't police every moment of their lives. So I don't think it's a terrible thing that he's done.

"But Ross has had an injury, he's still kind of carrying an injury, there's a bit of pain on shooting.

"So he just has to work his way back in, in terms of the fitness thing, and train well. And I certainly don't hold anything against my players.

"I like Ross, he's certainly one of my players. And he needs now to show all his reactions on the pitch."

In September, Lampard labelled Barkley "naive" when photos of the midfielder appearing to argue with a taxi driver, having apparently spilt chips in the back of a cab, were published ahead of the Blues' Champions League trip to Lille.

Chelsea can secure safe passage to the last 16 with victory in Spain, while Valencia can do the same should the hosts prevail.

The Blues lost their opening Champions League clash to Valencia 1-0 back in September, with Lampard admitting that defeat now leaves Chelsea facing in effect a knockout clash in Spain.

"The loss in the first game put us in this position," said Lampard.

"I don't think the Ajax draw did, it was losing a game at home on day one, when we should have got a result for sure.

"So what we've done really is bring that knockout football slightly earlier in the competition. That's no big problem.

"Obviously it will be a problem if we lose but the reality is at this level you're going to come to that kind of conundrum at some point where it will be like this, so that is a big test for us."

Asked if Lampard will learn a lot about his young squad at the Mestalla, Lampard added: "I think so. I will, we will.

"They've shown in a lot of moments over this season they're up to certain challenges.

"The Champions League has given us different ones because if anybody's going to take a group like this lightly they'll be quickly addressed to know how difficult this level of football is.

"Losing the first game against Valencia gave us difficulties. It's meant we've had to go to two difficult stadiums and win.

"But a lot of work remains to be done, so it's another challenge in front of them."