6. We lost \( \qquad \) of our best players due to injury. (to, too, two)

In this case, "too" is the correct choice. The word "too" is an adverb meaning "also" or "excessively," making it clear that the loss of players is an unfortunate situation affecting the team's performance. If you're ever unsure about which word to use, try substituting it with "also." If it makes sense, then "too" is likely the one you want. Remember that "to" shows direction or intention, and "two" refers to the number 2—small distinctions can make a big difference!