HRT on Tuesday did not reveal the identity of its race drivers for this weekend's Japanese grand prix.

HRT on Tuesday did not reveal the identity of its race drivers for this weekend's Japanese grand prix.

Sakon Yamamoto, who earlier this year replaced team regular Karun Chandhok, sat out the recent Singapore round with what the struggling Spanish outfit said was food poisoning.

Reserve driver Christian Klien stepped into the cockpit, impressing with his pace despite admitting the Singapore outing was a "one-off".

The Austrian's Singapore GP teammate Bruno Senna has also sat out a race this year - July's British grand prix - amid speculation HRT is selecting its drivers based on their current financial endowments.

The uncertainty about HRT's Suzuka lineup was triggered on Tuesday, when the team's traditional pre-event press release did not mention any of the team's contracted drivers Yamamoto, Klien, Senna or Chandhok.

"The Spanish team is eager to keep on improving and showing another positive performance," read the statement.

The statement's only quote was attributed to boss Colin Kolles.

"After our unfortunate race in Singapore, we look ahead and want to bring both cars to the finish line again," he said.

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HRT driver lineup unclear for Suzuka