Joba over Hughes

The 2010 Yankees will have C.C. Sabathia, A.J. Burnett, Andy Pettitte, and Javier Vazquez in the starting rotation. This leaves Joba Chamberlain and Phil Hughes to compete for the final spot in the five man rotation. All signs indicate Hughes ends up in the bullpen and Joba gets the chance to start.

In 2007 Keith Law of ESPN and Carlos Gomez of Hardball Times ranked Joba over Hughes. This was the season Joba burst in MLB with nearly unhittable performances coming out of the bullpen and Hughes showed promise in late season starts.

In 2008 the Yankees gave both the chance to start. Joba did well and ended up in the bullpen to close the year out due to innings restrictions, the infamous "Joba Rules". Hughes struggled and landed on the disabled list for a large part of the season.

In 2009 Joba was a key part of the rotation throughout the year. Hughes began the year as a starter and struggled before he settled into a set-up role for Mariano Rivera. Hughes seemed to blossom in this role.

So in the two years since both emerged as potential members of the Yankees rotation, Joba performed and only moved into the bullpen when pitch counts called for rest whereas Hughes got injured and landed in the bullpen due to poor performance. The scouting reports on both players are good, but the signs are all there that the Yankees are committed to Joba remaining in the rotation like he did in 2009. Keith Law now suggests the franchise signaled one belongs in the bullpen; I presume it to be Hughes.

Looking at statistics from Baseball-Reference.com, both players have better numbers as relievers by virtue of the challenge posed when a starter faces batters multiple times after pitching for far longer:

Joba Chamberlain G   IP SO/BB   BA  OBP  SLG  OPS ERA WHIP
     as Starter 43 221.2 2.04 .266 .351 .407 .759 4.18 1.48
    as Reliever 50  60.0 3.95 .182 .255 .257 .512 1.50 0.98

Phil Hughes      G   IP SO/BB   BA  OBP  SLG  OPS ERA WHIP
     as Starter 28 141.1 1.90 .265 .341 .436 .778 5.22 1.43
    as Reliever 44  51.1 5.00 .172 .228 .228 .456 1.40 0.85

Side-by-side, Joba has slightly better starter statistics and Hughes has better reliever statistics:

as Starter             G   IP SO/BB   BA  OBP  SLG  OPS ERA WHIP
    Joba Chamberlain  43 221.2 2.04 .266 .351 .407 .759 4.18 1.48
    Phil Hughes       28 141.1 1.90 .265 .341 .436 .778 5.22 1.43

as Reliever            G   IP SO/BB   BA  OBP  SLG  OPS ERA WHIP
    Joba Chamberlain  50  60.0 3.95 .182 .255 .257 .512 1.50 0.98
    Phil Hughes       44  51.1 5.00 .172 .228 .228 .456 1.40 0.85

The numbers suggest Joba holds up better facing opponents multiple times in a game:

Joba Chamberlain  PA SO/BB   BA  OBP  SLG  OPS
     1st  PA in G 628 3.16 .237 .303 .334 .637
     2nd  PA in G 357 1.60 .257 .368 .443 .811
     3rd+ PA in G  62 2.71 .222 .306 .370 .677

Phil Hughes       PA SO/BB   BA  OBP  SLG  OPS
     1st  PA in G 438 3.02 .201 .284 .307 .590
     2nd  PA in G 244 1.59 .304 .370 .495 .866
     3rd+ PA in G  98 1.50 .281 .340 .416 .756

Hughes has an advantage when batter faced one time, which works fine for relievers:

1st PA in G       PA SO/BB   BA  OBP  SLG  OPS
Joba Chamberlain  628 3.16 .237 .303 .334 .637
Phil Hughes       438 3.02 .201 .284 .307 .590

As batters face them again in the same game, Joba does better:

2nd PA in G       PA SO/BB   BA  OBP  SLG  OPS
Joba Chamberlain  357 1.60 .257 .368 .443 .811
Phil Hughes       244 1.59 .304 .370 .495 .866

3rd+ PA in G      PA SO/BB   BA  OBP  SLG  OPS
Joba Chamberlain   62 2.71 .222 .306 .370 .677
Phil Hughes        98 1.50 .281 .340 .416 .756

The difference is best demonstrated on pitch numbered 51-75, the pitches required for successful starters:

Pitch 51-75         G  PA   BA  OBP  SLG  OPS
     Chamberlain    41 249 .237 .359 .401 .760
     Hughes         28 157 .304 .372 .428 .799

Simply put, Hughes made better use of his time as a reliever than as a starter and Chamberlain made better use of opportunities to start than Hughes did.