Kean felt Junior Hoilett was fouled in the build-up to Branislav Ivanovic's strike before Nicolas Anelka hit the second, also from a corner.
"We're disappointed because normally we're very, very good at defending set plays," he said.
"We felt that they were sloppy by our standards.
"We felt there might have been a little bit of a foul on Junior Hoilett just before the corner that led to the first goal.
"But even taking that aside, we're normally aggressive on the first phase of our defending so I'm disappointed with the goals that we lost."