We present direct numerical simulations (DNS) of uniform flow at subcritical Reynolds number past a flexibly-mounted rigid cylinder subject to vortex-induced vibrations (VIV). We investigate different nominal reduced velocities near or in the region of maximum amplitude response for a small mass ratio and zero structural damping. We compute the correlation length of the flow quantities in the near wake and relate it to the force correlations along the cylinder. We perform a complex demodulation analysis to quantify the phase difference between structural displacement and forces. There exists a reduced velocity region near the 8trouhal frequency, for which a sharp drop in the spanwise correlation of the flow quantities in the near wake and the forces is observed. This decrease in the spanwise correlation corresponds to a poor phasing between displacement and forces but it does not preclude a large response from the structure.