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We propose a low-complexity soft detector for coded MIMO systems, which generates soft information by combining the hard-decision maximum likelihood (ML) estimate with the soft information generated by the minimum mean square error (MMSE) detector. The hard-decision ML estimate is produced by a modified MMSE based sphere decoder (MMSE-SD). The MMSE-SD is desired since it has lower average and worst-case computational complexity than the zero-forcing (ZF) based SD (ZF-SD) and can be used for arbitrary MIMO configurations. The proposed modification simplifies the implementation of the MMSE-SD, and it can be efficiently implemented by previously proposed complex ZF-SD architecture with minor modification. Our soft detector offers a low-complexity alternative when list based soft detectors are not affordable.