A disappointed Christian Klien on Wednesday vowed to keep pushing for a role in Formula One this year.
The Austrian was in contention for the final race seat on the grid with HRT, but the Spanish team announced that Vitantonio Liuzzi has inked the deal.
Klien, who impressed with HRT on his few outings last year, admitted he is disappointed.
"Still, we must keep our heads up and go forward," he said.
"I have said before that F1 is still the goal, and if the race seat does not work out, I will push hard for a third driver role with a clear perspective to run F1 races again sometime soon," added the 28-year-old.
"It is not the happiest day of my F1 career but then again it is by no means the end of all days."
Although Liuzzi insisted recently he is not a pay-driver, Klien's manager Roman Rummenigge hinted there was a "financial side" to the selection of the second HRT driver.
"We have worked very hard all winter long to create an attractive sponsorship package which is quite a challenge in the current international economic climate," he said.
"We were in very detailed negotiations with Dr Kolles up until yesterday. At the end of the day all our efforts were not enough to be on the grid in Melbourne," added Rummenigge.