Jose Antonio Espinosa, of the MX Onda team, was taken to hospital in Madrid and was in a coma after sustaining severe head injuries in the accident.
Race official Fernando Casillas was also in hospital suffering from trauma and facial bone fractures.
Responding to a report in the French sports newspaper L'Equipe that he was to retire, the 31-year-old Scot said on Saturday: ``I am reconsidering because I have been heartened by two things.
``With a minimum of training I am recovering some form, and also because I have seen that there is to be a test to detect EPO (erythropoetin).
``That test could prevent a further false rise in standards, so it may be worth continuing. The drug-taking problem has to be sorted out sometime.''
Obree said in L'Equipe that one reason he had considered retiring was because of the use of banned drugs.
EPO speeds recovery by increasing the red cells in the blood. Its use is forbidden.
Apart from the virus which caused Obree's withdrawal from two world championships, there was another setback last week when the Union Cycliste Internationale, the sport's governing body, decided to restrict the size of handlebar extensions.
It effectively bans Obree's extended racing position which helped him regain the world 4,000 metres pursuit title last year, and was copied by riders to win Olympic and world golds.
Obree, who is starting a business to market handlebars, is due to return to racing on Oct 29 at a track meeting in Geneva.