Given the symptoms described, the most likely field impression would be B: Ruptured spleen. The combination of lethargy, nausea, guarding of the abdomen, and left shoulder discomfort could indicate internal bleeding, especially with the presence of shoulder pain (Kehr's sign), which can occur due to irritation of the diaphragm from blood in the peritoneal cavity. Rupture of the spleen is a common cause of intra-abdominal bleeding in cases of blunt trauma, such as might occur during a soccer game.
