Background Mechanical low back pain is commonly treated by a physical therapist and involves the assessment of red flags that may warrant referral. Case Presentation A 42-year-old man presented with acute low back pain that started after strenuous rugby practice. Outcome and Follow-Up Examination revealed restricted active range of motion in right sidebending and rotation, and a negative neurological examination for motor weakness, altered reflexes, or sensory impairment. Upon initial evaluation, the patient did not present with abnormal vital signs or respiratory signs or symptoms, so this system was not assessed. Two days after the evaluation, the patient developed malaise, fever, and cough with bloody sputum. Discussion This presentation alarmed the physical therapist, and the patient was referred to the emergency department. A computed tomography scan revealed moderate pneumonia in the lower right pulmonary lobe. Recognition of red flags is imperative in a direct-access setting, as it improves clinical efficiency and directs appropriate intervention. JOSPT Cases 2021;1(2):73–77. doi:10.2519/josptcases.2021.9972