Is "weekend warrior" derogatory?

Often in sports I hear of the "professionals" and the "weekend warriors" (people who otherwise have non-sports related jobs and work hard on the weekends to train themselves to participate).

I can't tell if this phrase is meant to be derogatory. Is it meant to mean "these people are warriors who, on top of everything, also train for their sport", or is it meant to mean "these people are just adding an interesting hobby on the weekends and aren't real contenders in this sport"?

Actually, no dictionary defines the expression as derogatory, for instance, from AHD:

weekend warrior n. Informal

One who enthusiastically engages in an activity or hobby on the weekends outside of regular employment:

• "Despite the dangers, wreck divers are typically weekend warriors who leave families and jobs behind to test themselves at two hundred feet down" (New Yorker).

The term is generally not derogatory, but, I have heard it used in a negative context.

I work in the medical profession and have often overheard the following conversation:

ER physician: Patient is a 44 year-old weekend warrior who tore his Achilles tendon playing basketball in the park.

Orthopedic surgeon: Have him follow up in my office after he gets an MRI. We'll evaluate for surgery.

In this context, weekend warrior isn't being used in admiration, but rather as an endictment of overstepping one's level of fitness with resultant injury. The tone of voice with which it's delivered is what adds the derogatory connotation.