Fernando Alonso is "devoid of injury" following his crash in preseason testing, McLaren chairman Ron Dennis said Thursday.

Dennis, however, said it is still too early to guarantee the Spaniard will be ready to start the season at the Australian Grand Prix on March 15.

"He is completely lucid. He wants to drive and test, but the doctors said 'if you want him to go to Australia it's best to rest him,'" Dennis said. "I cannot foresee any reason why (Alonso won't be ready), but I am not the doctor. It's not for me to say yes or no."

Alonso is missing the final preseason test after he crashed on Sunday at the Barcelona-Catalunya circuit. He spent three days in the hospital before going home to recover.

Dennis said that his hospital stay was due to the extra attention all types of head injuries are receiving in sports.

Dennis said that Alonso did briefly loose consciousness and experience "some loss of memory" afterward but that early symptoms that pointed to Alonso having a concussion were not confirmed later by medical exams.

"He had a completely clear CT scan and a completely clear MRI, and through no stage of his hospital stay was there any indication of damage to his brain," Dennis said. "He is not even concussed. The technical definition of a concussion you can see in a scan."

Dennis said he contacted governing body FIA to initiate the investigation into the accident. He added that data retrieved from the car has ruled out a malfunction and repeated McLaren's theory that gusting winds caused Alonso to lose control and slam into the wall at Turn 3.

Jenson Button was back behind the wheel for McLaren on Thursday during the first of the final four days of testing. Reserve driver Magnussen will replace Alonso on Friday.

Dennis said that if Alonso wasn't ready to race in Melbourne then Magnussen would get the nod.

Alonso's accident came during a difficult winter for McLaren, which has switched to Honda engines this season. It has had problems both with reliability and speed.

Dennis said his team was "still at the foot of a steep mountain."