Osgood-Schlatter disease: This condition is characterized by inflammation of the patellar tendon at its insertion on the tibial tuberosity, which matches the patient's symptoms of tenderness over the right tibial tuberosity. The patient's age and participation in soccer also align with the typical demographic for Osgood-Schlatter disease.

Tibial stress fracture: Stress fractures can occur in athletes, especially those involved in sports with repetitive running and jumping, like soccer. The location of the pain and the patient's activity level make this a plausible diagnosis.
Chondromalacia: This condition, also known as runner's knee, involves the softening of the cartilage on the underside of the kneecap. It's common in adolescents and young adults who are active in sports, which could explain the patient's knee pain.

Dislocated patella: Although less likely given the specific location of tenderness, a dislocated patella could cause significant knee pain and should not be overlooked due to its potential for serious complications if not properly treated.
Baker cyst: A Baker cyst, or popliteal cyst, could cause pain and swelling in the back of the knee. While the primary complaint is tenderness over the tibial tuberosity, a Baker cyst could potentially refer pain to this area or coexist with other conditions.

Tumor or infection: Although rare, conditions such as osteosarcoma or osteomyelitis could present with localized bone pain and should be considered, especially if the patient does not respond to initial treatment or if there are systemic symptoms such as fever or weight loss.
Other rare bone or soft tissue tumors: Conditions like Ewing's sarcoma or benign tumors could also cause localized pain and should be kept in mind, particularly if the diagnosis remains unclear after initial evaluation.