A Deivid own goal put the Blues ahead in Istanbul but former Bury striker Colin Kazim-Richards equalised and Deivid made amends with a 25-yard cracker to give the Turkish side a surprise 2-1 win.

Ballack told Sky Sports 3: "We are very disappointed because we had a good chance to win here. In the first half we controlled things but we gave them the chance to come back.

"Even after they equalised we had good chances - me and Didier (Drogba) - but we lost concentration.

"It was our fault. A long ball changed the game and then a fantastic shot from 25 metres."

Chelsea's away goal could prove crucial in the second leg, and Ballack believes they can turn the tie around - although he is wary of Fenerbahce's goalscoring threat.

"We are strong enough but we have to concentrate over 90 minutes," Ballack added. "After it was 1-0 they took many risks, attacked with seven or eight players.

"We saw (in the previous round) against Sevilla they can score away from home but it is in our hands."

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Chelsea coach Avram Grant tried to put a positive spin on the result.

"We dominated the game; we created chances - but this is football," he told Sky Sports 3.

"Normally it's a good result to lose 2-1 away from home - but because we played the better football, we are disappointed."

Grant feels his side can turn things round in the home leg against the Turks, who are playing in their first Champions League quarter-final.

"I feel good. I feel if we play like we did most of the game we can win," he added.

Frank Lampard returned to the side after missing England's defeat in France and Chelsea's win over Middlesbrough through illness.

The midfielder appeared unhappy at being substituted with quarter-of-an-hour to go, but Grant insisted there are no problems between the pair.

The Blues boss said: "After he was sick, he was not ready to play 90 minutes. He played well - he did everything that he could."