Today's "MLB Quiz of the Day" kicks off a new series in which we will test your knowledge of the best big league player to wear each uniform number, based on WAR, courtesy of Baseball-Reference.

An important note before getting started: A player is only considered eligible for whichever number he wore for the most seasons during his career. For example, Roger Clemens would be considered only for No. 21, which he wore for 15 seasons, and not for No. 22 (nine seasons) or No. 12 (one season). That said, this quiz isn't designed to test your knowledge of how many seasons a player wore a certain number, so operate under the assumption that if a player is listed as a possible response, then he is indeed eligible for that specific number.

We begin with Nos. 0-9 below, but come back Friday when we tackle Nos. 10-19: