Transient Signal Analysis (TSA) is a Go/No-Go device Testing method that is based on the analysis of voltage Transients at multiple test points. In this paper, a technique based on an extension to TSA is presented that is able to predict critical path delay using data from non-critical (predictor) path tests. A characterization phase is performed a priori in which both predictor path and critical path delays are measured from a set of defect-free devices. The characterization data is used to define the relationship between the power supply transient signal data and the actual delays. Once established, prediction is performed during production test by simply re-analyzing the data from the predictor path Go/No-Go TSA tests, and therefore, no speed bin testing is required. Simulations on an 8-bit multiplier are used to demonstrate a linear relationship between a range of supply rail Fourier Phase harmonics and delay under various process models. The accuracy of the prediction is evaluated statistically against the measured delays from an additional set of critical path simulations.