I am a huge believer in playing mutiple sports. Some people don’t agree with it but I think it is very valuable to any athlete.
On the positive side, I think you learn things about yourself in multiple sports that you normally wouldn’t just playing one. You learn how you can respond to different pressure situations and what kind of player you really are. I played QB and I pitched in high school and I felt that pitching helped me deal with the pressures of playing QB and vice versa. I feel that could be the same with other sports as well. Not just the mental side will develop but the physical side too. If you are a basketball and football player, you are going to have great endurance from basketball and you will be a physical player from football. I think a lot of sports go well together. Perfect example, Josh Rosen was a tennis prodigy growing up, tennis Develops your rotational force and hip drive. That is why Rosen is such a pure passer.
I don’t really see the negatives other than a coach wants you to focus on one thing. I guess that’s a negative but I really believe playing multiple sports will be good for you and help your game improve. But if you are that guy who needs to only take one thing at a time, you probably shouldn’t. Or if football is your passion but you need to get dramatically better, you should probably take a year off and just work. It all depends the athlete, but I am a believer in it.