Barry Zito has arrived. He stepped on the mound against the Twins in Game 3 widely recognized as one of the elite pitchers in the game. His 2002 regular season performance may not make him the automatic AL Cy Young Award winner, but it has put him on the short list of contenders for the honor, along with the Red Sox 1-2 punch of Pedro Martinez and Derek Lowe.

But as highly acclaimed as Zito is, is it possible he's even better than we think? One factor that often gets overlooked in player evaluation in general, and the AL Cy Young discussion in particular, is the impact of the unbalanced schedule. And that's an area where Zito seems to be operating at a big disadvantage. Pitching in the hitting-rich AL West, Zito made 13 of his 35 starts against the Mariners, Angels, and Rangers, while Lowe made only four starts against that group. Meanwhile, pitching in the offensively mixed AL East, Lowe made nine of his starts against Tampa Bay and Baltimore, while Zito made only four starts against that gruesome twosome.

I'm not the first person to bring up Zito's tougher schedule; ESPN.com's Matt Szefc and David Schoenfield, among others, have pointed it out. But highlighting the issue really just raises a bunch of questions: Exactly how tough was Zito's schedule relative to those of Lowe, Martinez, and the rest of the league's pitchers? And how much difference does it make? If we attempt to level the playing field by adjusting for opposition quality, is that adjustment enough to elevate Zito above his competition?

We'll measure a pitcher's toughness of schedule by averaging the run scoring ability of the teams he faced, weighted by the number of times he faced them. The run scoring numbers are park-adjusted, so we're not fooled into thinking that the Rockies have one of the the top offenses in the league.

Of course, figuring out offense quality is a circular problem: if the quality of a pitcher is dependent on the mix of offenses he faces, then the quality of an offense is dependent on the mix of pitching staffs it faces. Fortunately, we can give this circular problem to a computer, and let it churn away until the results converge (which they do, really quickly). I won't go into any more detail than that here, much to your great relief I'm sure.

Here are the 10 toughest and 10 easiest schedules faced by major league ERA qualifiers in 2002. Schedule Difficulty is given in terms of percent above or below league average. So for example, the average offense faced by Tanyon Sturtze scored 4.9 percent more runs than an average AL team.

                            Schedule
    Pitcher         Team   Difficulty
1.  Tanyon Sturtze   TAM     +4.9
2.  Mike Hampton     COL     +4.1
3.  Jason Jennings   COL     +4.1
4.  Joe Kennedy      TAM     +4.0
5.  Tim Hudson       OAK     +3.6
6.  Cory Lidle       OAK     +3.6
7.  John Thomson   COL/NYM   +3.6
8.  Sidney Ponson    BAL     +3.3
9.  Rodrigo Lopez    BAL     +3.2
10. Miguel Batista   ARI     +2.8
...
76. Roy Oswalt       HOU     -2.3
77. Roger Clemens    NYY     -2.5
78. Jon Garland      CHW     -2.6
79. Glendon Rusch    MIL     -2.6
80. Eric Milton      MIN     -2.7
81. C.C. Sabathia    CLE     -2.8
82. Chuck Finley   CLE/STL   -2.9
83. Matt Morris      STL     -2.9
84. Ryan Dempster  FLA/CIN   -3.1
85. Mark Buehrle     CHW     -3.3

It's not hard to figure out what's going on here. The pitchers who faced the toughest schedules are all from divisions containing top-flight offenses -- the AL East (Yankees, Red Sox), the NL West (Giants, Dodgers), and the AL West (Mariners, Angels, and Rangers). Just as importantly, they all play for teams with weak offenses relative to their division, so they don't have a chance to boost their numbers against their own weak teammates. For Sturtze and Joe Kennedy, having to face the Yankees and Red Sox six or seven times is bad enough; not getting a chance to face the Devil Rays "hitters" even once makes things worse.

The pitchers with the easy schedules tell pretty much the opposite story. They're almost all from the two central divisions, which are heavy with weak-hitting teams. And most play for relatively strong offensive teams, so they avoid one potential tough opponent entirely.

Zito had the 13th toughest schedule in the majors; the average offense he faced was 2.4 percent better than league average. Lowe was 55th on the list, with an average opponent 1.1 percent worse than average. Martinez was right in the middle of the list (40th), with an average opponent just a hair above average. So as we suspected, Zito did pitch against tougher opponents than his Cy Young competitors, although the schedule disparity was not as wide as I thought it might be.

And how much difference does that schedule disparity make? We can find out by adjusting the pitchers' run prevention numbers for opposition quality. We'll look at a measure of Runs Above Replacement -- how many runs the pitcher prevented beyond what a replacement level pitcher would have allowed. We'll do the opposition adjustment (and the park adjustment) game-by-game.

Here are the top 10 in the AL in schedule-adjusted Runs Above Replacement (RAR/SA). The first column shows Runs Above Replacement without the schedule adjustment, so you can see how much difference correcting for opposition quality makes.

Pitcher        Team    RAR    RAR/SA
Derek Lowe      BOS    71.4    70.4
Tim Hudson      OAK    62.4    68.6
Barry Zito      OAK    64.6    67.4
Pedro Martinez  BOS    61.8    62.7
Roy Halladay    TOR    58.3    62.2
Jarrod Washburn ANA    54.0    54.6
Jamie Moyer     SEA    49.8    51.8
Mark Buehrle    CHW    50.2    46.6
Mark Mulder     OAK    42.2    46.0
Ramon Ortiz     ANA    39.5    45.6

Adjusting for schedule difficulty does narrow Lowe's advantage, but surprisingly it's Zito's teammate Tim Hudson who makes up most of the ground. Hudson faced an even tougher schedule than Zito in 2002, tough enough to push him over Zito in the run prevention standings.

The AL Cy Young race is a close one, and accounting for opposition quality only makes it closer. There are decent arguments for any of the top four guys on the list above. I went with the run prevention numbers and gave my Internet Baseball Awards vote to Lowe.

So Zito gets to try to pitch his team to the World Series, while Lowe gets the honor of some guy on the internet supporting him for the Cy Young. Somehow, I suspect Zito will take that trade.

You can check out more work from the team of writers of the Baseball Prospectus at baseballprospectus.com. Michael Wolverton can be reached at mjw@baseballprospectus.com. Baseball Prospectus is a registered trademark of Prospectus Entertainment Ventures, LLC.