Former Colorado Rockies Pitcher Jason Hirsh, radio personality Andy Lindahl on youth baseball coaching, sport specialization

Even USA Baseball agrees with the benefits of playing multiple sports, such as avoiding burnout and reducing the risk of overuse injuries. Now, that being said with a caveat as stated by Hirsh. “Once you get into high school, you need to start honing your skills,” said Hirsh.
He went on to expand by stating if you’re wanting to focus on baseball, for instance, you need to play other sports that are more an extension of your training program than one that has no correlation to your sport of choice, such as track for conditioning and flexibility that correlates to speed, reaction time and leaping ability if you are an outfielder/middle infielder (see Dexter Fowler).
Or football for core/arm/lower body strength, speed, and toughness for really any position on the field, bonus of arm strength without the overuse of pitching/throwing year-round if you are a QB (e.g. Ryan McMahon).
A lot of other people I have heard arguments that you MUST specialize your child in a sport if you ever want them to get that full-ride scholarship.
Jason Hirsh warned when asked if there was any validity to that, he flat-panned “[n]ot at all.” He continued, “[u]nless you are a freak of nature, you are not getting a full ride. If you are looking for a full-ride scholarship, and you’re not a freak of nature, like a Mike Trout, you chose the wrong sport.”
He went on to explain that in today’s college landscape, academics are as important, if not more important than athletics. As Hirsh noted, “Tommy Try Hard” is going to need to either have academic scholarships to offset the cost, or a family that can foot the bill as they work through college.