Performance degradation of an IEEE 802.11g network is studied in case legacy stations are associated with the AP. Custom event-driven simulator was developed for the purpose. We demonstrate its consistency by comparing the outputs with a widely accepted network simulator and with results of an analytical study. Performance degradation is analyzed in terms of access delay and throughput. We study the effect of an associated legacy node on access delay as a function of number of nodes in the network. Additionally, we focus on a fixed size network and examine the effect of the bit rate used for transmission of protection mechanisms' control frames. Significant performance drop is observed both in terms of access delay and throughput.