Briton Nielsen only moved to Caterham in December 2011.
Toro Rosso driver Daniel Ricciardo said this week that he is confident about the Red Bull-owned team’s 2013 plans.
“But even if they tell me [the 2013 car] is the best thing since sliced bread, I’m not going to get too excited until I drive it and feel comfortable myself.
“But we’ve definitely got good expectations,” he told the Faenza based team’s website.
Toro Rosso finished the 2012 season in ninth place, ahead only of F1’s non-scorers Caterham, Marussia and HRT.
Subbed by AJN.