Hernandez, known as Chicharito meaning Little Pea, was taking a short-cut to the Carrington complex near Manchester in his 4x4 when he met the tractor.
The 22-year-old Mexican, who scored the only goal in United's Champions League win over Valencia on Wednesday, was forced to give way eventually.
United's youth team director Brian McClair told the club magazine: "It's a single track road with ditches on either side.
"The farmer had right of way but Chicharito was not for reversing, until the tractor was about to drive over his car.
"He finally decided to retreat, nearly ending up in the ditch and then up a telegraph pole. The farmer was not amused."