Leonard Fournette Speeding, Racing Motorcyclist Before Car Fire, Witness Told Cops

Leonard Fournette was driving like a madman before his car burnt to a crisp last month ... moving at high rates of speed and racing a motorcyclist -- at least, that's according to a new police report, obtained by TMZ Sports.

In the Florida Highway Patrol documents ... cops say a witness came to them with the allegations shortly after Fournette revealed his car had been destroyed while on a Hillsborough County highway on June 27.

In the docs, cops say the witness told them he had been driving northbound on I-275 ... when Fournette's black Dodge passed him "at a high rate of speed."

The witness, according to the report, then stated "he observed the vehicle and [a] motorcycle to be racing and changing lanes." He stated he observed the vehicles "racing when fire then erupted from the bottom of" Fournette's car.

In the report, cops state the witness told them Fournette then slowed down and pulled over -- while the motorcyclist kept on moving.

Fournette, however, told a much different story to cops ... in the report, officers say the NFL star "stated he has been having problems with the vehicle as of late" -- before it erupted in flames on the 27th.

Fournette -- who had seemed to love the car, posing inside of it in one recent social media post -- said of the incident on his Instagram page, "Man it was one of those days today, but I would like to thank God, my car caught on fire while I was driving, But I am still blessed."

We've reached out to Fournette for further comment, but so far, no word back yet.