Well, nothing about Pat Burrell was especially average or boring. He was a three-true-outcome guy who usually didn't have to worry about running too hard because he was either jogging to first base, jogging around the bases, or walking slowly back to the dugout after a strikeout.
But when it comes to bWAR -- not a flawless metric, but surely one of the best metrics that can be distilled into a single number -- Pat Burrell was the midpoint between the first-ballot Hall of Famer that every team thinks they're getting with the first-overall pick and the pain that comes with the complete busts. From Baseball Reference on first-overall picks:
47 matching player(s). 41 played in the majors (87%). Total of 799.2 WAR, or 19.5 per major leaguer.
That number could get a boost if/when Bryce Harper and/or Gerrit Cole arrive in the majors, but until then Burrell's 18.7 bWAR is about as average as can be for a first-overall pick in the amateur draft. It's far from the Hall of Fame dominance of a player like Alex Rodriguez, Chipper Jones, or Ken Griffey Jr, but it hints at exactly what Burrell was -- an often productive, flawed player who was good enough to get a few MVP votes, but never good enough to make an All-Star team.
Even though your image of Burrell's defense might be the exact same one I have -- that of a man with radiation poisoning who can't get his foot out of a gopher hole -- his defensive numbers weren't that bad. He came, he slugged, he lumbered, and now he's heading off into the void.
He wasn't a once-in-a-generation slugger. He wasn't a washout who couldn't even make the majors for a cup of coffee. He was Pat Burrell, Average First-Overall Pick. There are worse things to be.