Jose Mourinho said he had to talk tough to his players at halftime before they came from behind to beat Porto 2-1 and reach the quarter-finals of the Champions League on Tuesday.

The English champions went behind to a 15th minute goal from Ricardo Quaresma and that prompted Mourinho to make an attacking tactical change to three at the back and to tell his players they had to enjoy the challenge.

"I made them think a bit," the master tactician said. He told them: "At the moment we are out of the competition. If we can enjoy the challenge let's enjoy it. If we are scared let's stay at home. We can show our personality."

He said Chelsea, with the imposing John Obi Mikel in place of a sluggish Claude Makelele, had risen to the challenge and shown strength of mind. "I thought that until the last second the game was open. In the second half we were the most likely to score but every time they had the ball we were in danger."

Dutch winger Arjen Robben levelled the score two minutes into the second half with a goal fumbled in by goalkeeper Helder. Porto coach Jesualdo Ferreira described it as a happy goal for Chelsea, an unlucky one for Porto.

Michael Ballack finished the job in the 79th minute with a hooked volley after a nodded pass from Andriy Shevchenko.

Ferreira said it was the sort of goal you did not see in the Portuguese league "from players who are very strong".

Ferreira praised his compatriot and former Porto coach Mourinho's tactical nous but added "It was a game either team might have won."

Mourinho said the Champions League was very open now. "Two of the last three champions (Porto and Barcelona) are out of the competition, Inter is out, Olympique Lyon the superteam is out. It's that sort of competition," he said.

"If we win the Champions League I don't think it would be a miracle but if we go out in the quarter-finals I think that would be a normal picture too."

Mourinho, who has been under pressure after disagreement with the Chelsea hierarchy since the new year, reiterated that he wanted to stay at the club, where he has a contract until 2010.

"If at the end of the season I have to leave, that's football. I want to continue. The club has a project to make the team the best in Europe by 2014. It is 2007. I still have work to do," he said.