  We study the dynamics of an asymmetric intruder in a glass-former model. At
equilibrium, the intruder diffuses with average zero velocity. After an abrupt
quench to $T$ deeply under the mode-coupling temperature, a net average drift
is observed, steady on a logarithmic time-scale. The phenomenon is well
reproduced in an asymmetric version of the Sinai model. The subvelocity of the
intruder grows with $T_{eff}/T$, where $T_{eff}$ is defined by the
response-correlation ratio, corresponding to a general behavior of thermal
ratchets when in contact with two thermal reservoirs.
