WARP measures the number of wins a player contributes above what a replacement-level player would provide in the same role and minutes. It is closely related to VORP conceptually; specific implementations vary (Basketball-Reference's version is based on BPM, while other implementations use different base metrics).
Replacement-level framing is analytically sound — comparing against a replacement player rather than zero provides a more realistic counterfactual. VORP is essentially APEX's version of WARP (displayed but not scored).
Cumulative metric — penalizes players who miss games through no fault of their own. "Replacement level" is a modeled concept, not a directly observable player type.
Not scored in APEX. VORP (which is BPM-based WARP) is used as a display-only metric in player cards. Scoring WARP or VORP alongside BPM would double-count the same signal. The replacement-level framing is conceptually embedded in APEX's GP^0.75 availability modifier, which applies a smooth availability penalty rather than binary replacement.