Hi Emily!
I think it's better not to force him to stick it out. He's clearly made up his young decision.
What I learned was once they began school AND sports, that the sports were not that much fun the WHOLE season. Signs: We had a few tears when it was time to go to practice/game. Turns out, he was just simply too tired from school, and just wanted to be in his own home. It wasn't about liking the sport, it was about not having enough time at home.
We took a whole year and half off from sports until my son was a little more "emotionally" ready for the whole sports thing. Baseball is coming up, so I'll let you know if it worked or not :o)
Now my older son, we never had any problems like this. Even at 4 & 5 years old, he wanted to play everything and loved all of it. With my youngest son, it's about getting him exposed to the sports only. I cannot tell if he will even play sports yet, like my older one.
I'd think about giving your son a break if he doesn't respond too well this weekend. He might not be emotionally ready yet.
Good Luck!
~N. :O)