The former Liverpool winger had his £25,000 watch stolen by thieves, armed with knives, hit his car and threatened the 20-year-old.
The incident took place in south east London at 1.45pm on November 6. The crime took place just four days after West Ham striker Andy Carroll was threatened at gunpoint on his way home from training.
A Met Police spokesman said: "One of the suspects threatened the victim with a knife before stealing his watch. The victim was not injured.
"At this early stage, officers are investigating whether the suspects intentionally collided with the victim's car".