Briscoe, who made his final IndyCar appearance of the year with the team at Sonoma on Sunday, had been hoping to do ALMS/IndyCar double duty in Baltimore this week.
However his ALMS team Level 5 cooled on the idea after the Australian injured his wrist in the second IndyCar race in Toronto.
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Panther had been using the balance of 2013 to evaluate drivers for next year after splitting with JR Hildebrand in May.
Team boss John Barnes told AUTOSPORT that he now has a preferred driver in mind, although no deal has been done. Widespread paddock speculation has Briscoe as the frontrunner for the ride.
“Oriol’s going to run for us for the rest of the year,” Barnes said. “We are going to test a couple of guys after the season is over as well for other opportunities, but I think we’ve got it figured out, what we’re going to do.”
Reports in Europe suggested that one of the drivers in line for a test could be former Toro Rosso Formula 1 driver Jaime Alguersuari, but Barnes refused to comment on whether he had been in contact with the Spaniard.