We discuss a non-intrusive methodology for concurrent fault detection in random combinational logic. The proposed method is similar to duplication, wherein a replica of the circuit acts as a predictor that immediately detects potential faults by comparison to the original circuit. However, instead of duplicating the circuit, the proposed method selects a small number of prediction logic functions which only partially replicate it. Selection is guided by the objective of minimizing the incurred hardware overhead at the cost of introducing fault detection latency. To achieve this, the proposed method replicates only a reduced width output function for every input combination, yet without compromising the ability to detect all faults. In contrast to concurrent error detection schemes which presume the ability to resynthesize the circuit, the proposed method does not interfere with the implementation of the original design. As compared to previous approaches, the proposed method achieves significant hardware overhead reduction, while detecting all faults with very low average fault detection latency.