The present invention provides methods for assessing the performance of one or more test olefin polymerization catalysts which comprise one or more metals. The methods are based on the use of coordinating-reactive quencher molecules that are added to polymerization reactions to tag oligomers and optionally to tag polymers that were bound to active catalyst at the time of quenching. The tag allows the identification and analysis of the molecular weight, length, and structure of oligomers and polymers generated by the activated catalyst as a function of reaction time as well as other polymerization process parameters. Evaluation of the presence or absence of tagged oligomers and polymers, the relative molecular weights, lengths and/or structure of the tagged oligomers and polymers and/or the determination of the relative or absolute amounts of tagged oligomer and polymers generated on quenching provide information which can be used to assess the performance of one or more activated polymerization catalyst.