Jose Mourinho has warned his Chelsea stars that finishing at the top of their Champions League group is no guarantee they will be able to make a serious challenge for the trophy.

Mourinho's side ensured it took first place in Group E with a 1-0 win over Steaua Bucharest on Wednesday, thanks to Demba Ba's first- half goal at Stamford Bridge.

But it was an underwhelming display from the Blues against a Steaua team which offered only token resistance and Chelsea boss Mourinho added to the downbeat mood by refusing to talk up his team's chance of emulating its 2012 triumph in the competition under Roberto Di Matteo.

Mourinho might have been indulging in a little 'kidology' to take the pressure off his players when he claimed he is unconvinced his squad is mature enough to win Europe's elite club competition.

Yet the Portuguese coach's words also contained more than a grain of truth in the aftermath of the latest spluttering performance in what has been an erratic start to his second spell in charge at the Bridge.

"We have to grow up step by step," said Mourinho.

"We now are going into matches that are new to some of my players.

"Some of my players didn't play any games in the knockout stages of the Champions League. They have played in group stages and the Europa League. It will be a different scenario for them.

"There are teams in better condition to win the competition, or at least be seen as the favorites: Bayern Munich, Barcelona and Real Madrid."

In theory, finishing atop the group will give Chelsea a less daunting opponent when the draw is made for the last 16.

The Blues will face either AC Milan, Zenit Saint Petersburg, Bayer Leverkusen, Olympiakos or Galatasaray, which features former Chelsea striker Didier Drogba.

But Mourinho, who would relish a clash with Drogba, is yet to be convinced that Oscar, Eden Hazard and Willian, his talented but inexperienced young playmakers, will be able to flourish under the intense pressure of a knockout tie against Europe's best.

"There are good teams who finished second," said Mourinho.

"Sometimes, of course, we look to the top ones and you see they are the main candidates to win the competition, but in the second position you have difficult teams.

"Milan is a possible opponent that has won the European Cup many times.

"You have the Russian champions. You have a German team in Leverkusen who are always very difficult and the Turkish champions with 'King Didier'.

"He deserves to come here and get a reception like I did when I returned.

"I know what I felt and I think he deserves that."

On the evidence of the lackluster effort against Steaua, which came just days after a shock 3-2 defeat at Stoke, Mourinho's rebuilding of Chelsea is still a work in progress.