Mike, a professional rugby player, was involved in a high-intensity match. During a tackle, he collided forcefully with an opponent and landed awkwardly on his left side. Immediately after the impact, Mike experienced intense pain and a noticeable deformity in his left chest area. He was unable to move his left arm without severe discomfort and noticed swelling and bruising over the injured site. Mike is likely to have sustained a fracture in his: