The Dallas Cowboys are losing a key member of their defense for the rest of the season. Linebacker Leighton Vander Esch has been ruled out for the rest of the year due to a neck injury, and his career is also in question. The 27-year-old was eligible to come off injured reserve this week but is still suffering lingering symptoms. He was injured in a loss to the San Francisco 49ers, and has a history of neck issues.