In this paper we address the decoding problem in the K-user MIMO interference channel assuming an interference alignment (IA) design. We aim to decode robustly the desired signal without having a full Channel State Information (CSI) (i.e. precoders knowledge) at the receivers. We show the equivalency between the IA model and the Semi-Blind Source Separation model (SBSS). Then, we prove that this equivalence allows the use of techniques employed in source separation for extracting the desired signal free of interference, even though dependency exists between some components of the source signal in the SBSS model. Our simulation results illustrate a BER performance very close to the MMSE receiver with full-CSI.