I agree that tendonitis should be treated aggressively, it can become a chronic nuisance undermining a players potential, I’m a chiropractor with physical therapy, sports medicine and science background. I’ve been in private practice for 15 years treating sports injuries in adults and youth athletes. I played baseball into the junior college level when I got sidelined from a shoulder throwing injury. The initial doctor I saw said “if it hurts don’t throw that way”! A definitive diagnosis needs to be made sooner than later, then treat accordingly. Tendonitis, ligament sprain / tear, growth plate issue, muscle strain or something above or below the joint should be ruled out. Is the pain on the inside or outside of elbow?. Does the player throw breaking pitches vs fastballs and change ups. These factors need to be considered in determining a diagnosis. I’ve seen all too often youth and high school athletes get inappropriate advice for their injuries and never rehab them properly which leads to additional mechanical problems. Players and parents need to be their own advocate.