[en] The advent of x-ray free electron lasers is providing new opportunities for probing the ultrafast excited state dynamics using structurally sensitive techniques. Herein we use excited state wavepacket dynamics of a prototypical Cu(I)-phenanthroline complex, [Cu(dmp)_2]"+ (dmp = 2, 9-dimethyl-1, 10-phenanthroline) to investigate how femtosecond vibrational and electronic relaxation is translated into transient x-ray absorption and emission. Using realistic experimental parameters we also derive the anticipated signal strengths for these transient features. This indicates that although recording a signal capturing the strongest transient (i.e. excited state–ground state) changes will be possible for all cases, only with x-ray absorption near-edge structure and extended x-ray absorption fine structure will it be possible to resolve the fine details associated with the wavepacket dynamics within realistic experimental acquisition times. (paper)