All four HRT drivers eligible to race - Klien (GMM) Christian Klien on Friday hinted he might appear on the formula one grid at the wheel of an HRT car in 2010.
At Silverstone, Bruno Senna was mysteriously dropped by the struggling Spanish team, replaced for the British event by test driver Sakon Yamamoto.
Austrian Klien, 27, is also a Hispania test driver.
When asked why Senna was sidelined at Silverstone, team boss Colin Kolles told the Australian broadcaster One-HD: "We have four drivers."
For now, Klien said he is hoping to make another appearance in the F110 car during Friday practice.
"What is planned for Hockenheim, I don't know," he said in an interview with motorline.cc.
"Who will sit in the car, I think, will be a short-term decision."
When asked if he might race at some point in 2010, as his Japanese test colleague did in Britain, Klien answered: "That, I don't know.
"First I am thinking about the Friday testing -- everything else is a team decision.
"Since the last race, it is the case that Hispania can nominate any of the four drivers for the race seat. And all four drivers are treated equally. After that, the decision rests with the team," he added.
Klien also confirmed that, despite earlier uncertainty about the future of Geoff Willis, the Briton is working on HRT's 2011 car.