Reigning MotoGP world champion Marc Marquez faces a race against time to start the defence of his title after breaking a leg in a training accident.

Spaniard Marquez sustained a break of his right fibula whilst riding a dirt-track bike in Lleida on Wednesday.

Marquez, who turned 21 on Monday, was then treated by MotoGP surgeon Dr Xavier Mir at Barcelona's Universitario Quiron Dexeus hospital.

Dr Mir said: "The results showed no ligament damage or dislocation and no need to proceed with surgery.

"I expect he will need three to four weeks to fully recover."

That rules Marquez out of the next two pre-season tests in Sepang, Malaysia, at the end of next week and Losail, Qatar, on 7-9 March.

Marquez, who was quickest on all three days of the first test at Sepang earlier this month, will also sit out a private Honda test at Phillip Island, Australia, in early March.

Despite the timeframe, it does put Marquez under pressure to ride in the opening race at Losail on 23 March.

Assessing the incident, Marquez said: "It was a really unfortunate accident that could happen to anyone at any time.

"I was rushed to hospital and Dr. Mir treated me, thankfully there was no ligament damage and it seems like a clean break."