An FPGA implementation requires a significant effort of the hardware designer, who optimizes FPGA designs by going through many time-consuming CAD flow iterations. These iterations provide two types of feedback: (1) the FPGA performance and (2) the identification of the parts having the highest impact on the FPGA performance. Both depend on the wirelength behavior. Studies have been dedicated to the estimation of local [5] and global [4] wirelengths, but to our knowledge both performance estimations and identification of the critical zone are not present in literature. Therefore this paper, firstly, presents a comparison of three performance estimation techniques: logic depth, Monte Carlo simulation and fast placement (ordered from low to high accuracy and runtime). Secondly, four methods identifying the critical zone are compared. Results show that Monte Carlo simulations provide a good identification of the parts having the highest impact on the performance. We conclude that Monte Carlo simulations provide useful feedback within a short runtime (about 30 times faster than placement), reducing the time-to-market of FPGA implementations.