A near infrared spectrophotometric (NIRS) sensor assembly for non-invasive monitoring of blood oxygenation levels in a subject's body is provided that includes a pad, at least one light source, a near light detector, a far light detector, and a cover. The light source is operative to emit near infrared light signals of a plurality of different wavelengths. The near light detector is separated from the light source by a first distance that is great enough to position the first light detector outside of an optical shunt field extending out from the light source. The far light detector is substantially linearly aligned with the near light detector and light source, and is separated from the near light detector by a second distance, wherein the second distance is greater than the first distance.