Nissan Motor Co.'s loss of its second executive since July is fueling concern that the pool of talent surrounding Chief Executive Officer Carlos Ghosn is drying up.

Tuesday's disclosure that Chief Planning Officer Andy Palmer will quit to lead Aston Martin Lagonda Ltd. came almost eight weeks after the president of Nissan's premium Infiniti brand jumped to Cadillac. Ghosn, who's also CEO at Renault SA, lost his chief operating officer at the French carmaker in 2013 and his communications head earlier this year.

The defections add to the challenges facing Ghosn, 60, a man so lauded for saving Nissan from near bankruptcy in 1999 that he drew offers to run larger automakers and starred in a comic book. Today, Japan's second-largest automaker is lagging behind key financial targets, and the Leaf electric vehicle he has championed since 2009 is contending with Tesla Motors Inc.'s popular Model S.