Chelsea outplayed Inter Milan throughout but still lost the last-16 first leg tie 2-1 in a pulsating match at the San Siro.
Inter had taken a third-minute lead through Diego Milito only for Kalou to level in the 51st minute.
No penalty: Kalou went down under the challenge of Walter Samuel
But Esteban Cambiasso restored Inter's lead four minutes later togive Jose Mourinho's side a slight edge going into the return leg atStamford Bridge on March 16.
But it could have been so different if Chelsea had been awarded a penalty minutes before the break.
Waved away: Samuel was the last man and would probably have seen red had the referee awarded a penalty
Kalou appeared to be felled by Inter defender Walter Samuel butSpanish referee Manuel Gonzalez refused Chelsea's appeals for aspot-kick.
The official was surrounded by Chelsea players at the half-time whistle and Kalou is adamant it was a clear spot-kick.
Losing control: Referee Manuel Gonzalez told Kalou he had lost control of the ball
'It was a penalty but the referee decided it wasn't so there is not a lot you can do about it' he said.
'I felt him touch my right leg but the referee told me that I did not have control of the ball any more when he touched me.
'ButI was about to shoot and if he touched me on the back of the leg itshould be a penalty or he should have booked me for diving.'
VIDEO: Kalou on Chelsea's defeat at the San Siro Chelsea will still be wondering how they lost a match in which they were far superior in all departments.
Butthe English club were boosted after the game when it was discoveredthat goalkeeper Petr Cech, stretchered off with what looked like a kneeinjury in the second-half, had in fact damaged his calf.
Goal-getter: Kalou equalised for Chelsea shortly after half-time
ButKalou believes his away goal could prove vital in the return leg inwest London, although he admitted it was hard to celebrate in front of his former boss. 'It is a good feeling to have the away goal,' said Kalou.'Now we have to work on that and try to score at the Bridge and notconcede.
'I was happy but it was difficult to celebrate scoring against Jos?ecause he's the manager who brought me to Chelsea and I have great memories of him,' the Ivorian added. 'It's not easy to celebrate scoring against the one who gave you the opportunity to be where you are.'
'Jose knew we were going to attack and keep theball. But they scored at the right moments and that made thedifference. We knew could control the game but we knew they could bedangerous on the break and that is what happened.'
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