This is actually a fairly difficult question, and is much more a brainteaser than a piece of baseball trivia. If you look at it from a pure baseball standpoint, you aren't going to get it (unless you guess).
Don't get too hung up on the baseball angle. This is first and foremost a lateral thinking puzzle that happens to be couched in a baseball framework.
The details of the puzzle all have to do with baseball, but the manner of relating them to one another does not.
<input type=button style="font-size: 9px;" value="Show Spoiler" onclick='if (this.value == "Show Spoiler") { document.getElementById("spoil1").style.display = ""; this.value="Hide Spoiler"; } else { document.getElementById("spoil1").style.display = "none"; this.value="Show Spoiler"; } '> <div id=spoil1 style="display: none;"><BLOCKQUOTE><hr>The ordering of the list is meaningful ... <input type=button style="font-size: 9px;" value="Show Spoiler" onclick='if (this.value == "Show Spoiler") { document.getElementById("spoil2").style.display = ""; this.value="Hide Spoiler"; } else { document.getElementById("spoil2").style.display = "none"; this.value="Show Spoiler"; } '> <div id=spoil2 style="display: none;"><BLOCKQUOTE><hr> ... but its elements are not necessarily unique. (Although the answer is.) <input type=button style="font-size: 9px;" value="Show Spoiler" onclick='if (this.value == "Show Spoiler") { document.getElementById("spoil3").style.display = ""; this.value="Hide Spoiler"; } else { document.getElementById("spoil3").style.display = "none"; this.value="Show Spoiler"; } '> <div id=spoil3 style="display: none;"><BLOCKQUOTE><hr> Only the first 16 elements of the list are shown. A complete list would be longer. <hr></div> <hr></div><hr></div>
<input type=button style="font-size: 9px;" value="Show Spoiler" onclick='if (this.value == "Show Spoiler") { document.getElementById("spoil11").style.display = ""; this.value="Hide Spoiler"; } else { document.getElementById("spoil11").style.display = "none"; this.value="Show Spoiler"; } '> <div id=spoil11 style="display: none;"><hr><BLOCKQUOTE>All the historical baseball trivia need to solve this problem is referenced here:
http://www.baseball-almanac.com/awards/aw_mvpw.shtml</BLOCKQUOTE> <hr> </div>
<input type=button style="font-size: 9px;" value="Show Spoiler" onclick='if (this.value == "Show Spoiler") { document.getElementById("spoil12").style.display = ""; this.value="Hide Spoiler"; } else { document.getElementById("spoil12").style.display = "none"; this.value="Show Spoiler"; } '> <div id=spoil12 style="display: none;"><hr><BLOCKQUOTE> The years a given player was active and his age are completely irrelevant. As are the players' teams. </BLOCKQUOTE> <hr> </div>