Eli McCullough was captured by the Comanches in 1849 when he was about 14-16 years old. This show takes place in 1915. That makes Eli about 80-82 years old. Pierce Brosnan is nearly 64 - he needs some adjustments to make him Eli's correct age. Instead of riding his horse, maybe a wheelchair?
I don't think the writers/producers/director did their math.
I don't think the writers/producers/director did their math.