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This work explores the effect of adding a timing driven functional decomposition step to the traditional field programmable gate array (FPGA) CAD flow. Once placement has completed, alternative decompositions of the logic on the critical path are examined for potential delay improvements. The placed circuit is then modified to use the best decompositions found. Any placement illegalities introduced by the new decompositions are resolved by an incremental placement step. Experiments conducted on Altera's Stratix and Stratix II device families indicate that this functional decomposition technique can provide average performance improvements of 6.1% and 5.6% on a large set of industrial designs, respectively.