Adding some fun to the story, it turned out that before the game the Boston announcer Joe Castiglione have given Nava some advice that former manager (and player) Chuck Tanner had passed along to him. In Tanner's own first at bat in the majors, he hit his first pitch for a home run, and ever since then told every rookie playing in their first game that they should swing at the first pitch "because you'll never get another chance."
Clearly, Nava took the advice well.
Since that points, he's had a respectable career. He stayed in the minors the following season, but has made it back up to the majors full-time the last two seasons, and is currently hitting a very solid .282.
But it's this at bat -- this first pitch -- that he'll always remember. You can see that on his face as the crosses home plate.
Here's the video from the game on Fox (which was broadcasting it nationally). Unfortunately, they do only a fair job, missing out on the point that it was not just his first at bat, which they do eventually note, but the first pitch he ever saw. They may not have mentioned, but now you know --