As far as I see, you have complete control of what type of cards you see as well as the extent of the notifications. Being customizable to that degree, I don't see how anyone could be overloaded with information they don't want.
As you said you do not care about when your team is playing or rather if you care, you will mark it down some other way and do not need Google's help with it so you most likely won't have that card "turned on".
If you care, but don't want to be interrupted by notifications specifically, then you'll either turn off notifications for that card, or if possible (the following is pure assumption based on the Jelly Bean notification priority options), you would set that specific card's notification priority to minimum, meaning it does not show up in your status bar and doesn't fire off any sound/vibration signals, but if you pull down on the status bar (meaning you are looking for information) it's there at the bottom of your notifications, completely unobtrusive.
I really doubt this is the case, from my experience with other Google products. On Google+ valuable screen real estate is devoted to telling me I could follow popular entertainment people, or trying to get me to chat, hangout, et al. My android phone is chock full of things I can't get rid of, things that start services which if turned off turn themselves back on, etc. To actually use android I had to finally break down and get a gmail account, and found that my youtube account switched irrevocably to gmail. I was not asked, and there was no undoing it.
Everywhere I turn with Google I am being forced into a Procrustean bed, and you tell me that everything with Google Now is totally configurable so that it'll fit me. Sorry, at this point I do not believe you.
As you said you do not care about when your team is playing or rather if you care, you will mark it down some other way and do not need Google's help with it so you most likely won't have that card "turned on".
If you care, but don't want to be interrupted by notifications specifically, then you'll either turn off notifications for that card, or if possible (the following is pure assumption based on the Jelly Bean notification priority options), you would set that specific card's notification priority to minimum, meaning it does not show up in your status bar and doesn't fire off any sound/vibration signals, but if you pull down on the status bar (meaning you are looking for information) it's there at the bottom of your notifications, completely unobtrusive.
Either way, it's the user's choice.