Modern surgery has optimized the operation, but not always the patient. Despite major advances in operative technique, anesthesia, imaging, surgical devices, and enhanced recovery pathways, the physiological readiness of patients before surgery remains insufficiently integrated into routine surgical decision-making. Many modifiable risk factors, including poor functional capacity, frailty, sarcopenia, malnutrition, anemia, smoking, psychological stress, and reduced cardiopulmonary reserve, are often documented but not systematically treated as actionable surgical risks. Prehabilitation offers a practical opportunity to transform the preoperative waiting period into an active therapeutic window aimed at improving resilience before the incision. This editorial makes the case for prehabilitation as a missing surgical vital sign: a measurable, modifiable, and clinically meaningful marker of readiness that should be routinely assessed before surgery and integrated into perioperative decision-making. Although evidence regarding prehabilitation remains heterogeneous, recent trials and meta-analyses suggest that its effectiveness depends on appropriate patient selection, individualized intervention, adherence, monitoring, and integration into surgical pathways. A structured model based on screening, risk stratification, targeted prescription, monitoring, and incorporation into shared decision-making may allow prehabilitation to move from isolated programs to standard perioperative infrastructure. Redefining surgical success beyond technical completion and short-term outcomes requires a shift from procedure-centered surgery to patient-readiness-centered surgery. Prehabilitation should become a visible part of surgical culture before the first incision is made.