Justin Masterson is a reliever.

At least on this team, Justin Masterson should be in the bullpen. 

At least after good health returns to the rotation as a whole (Daisuke, Smoltz).

This isn’t a Joba debate either.  The Yankees could very well use a dominant reliever.  And even with that said, Joba Chamberlain’s long term value is still highest as a starter. 

And Justin Masterson isn’t Joba.  Masterson is projected to be closer to an average starter, Joba could be great.  Really great.

Masterson’s problems–the same that he had in the Minors–still exist.  Problems that will be exposed more often while starting, rather than in the relief role.

He couldnt’ retire lefties, not well enough anyway.  And he always ran into problems the more he faced a lineup within a given game. 

Masterson’s career ML splits:

vs RHB:  .203/.280/.300

vs LHB:  .263/.370/.419

There is a problem there.

Justin Masterson is dominant against right-handed hitters.

But lefties reach base well over the league-average.  Meaning that Masterson will have trouble until he can establish an “out-pitch” to retire them.  Or develop his command more so, which is a possibility.  Because currently, Masterson still catches too much of the inner half of the plate, at least against left-handers. 

And 2009 hasn’t been any different either.  A relatively small sample, but Masterson’s .794 OPS against lefties just isn’t going to cut it. 

And as for his difficulties the second and third time through the order (OPS, by inning)…

1st: .631
2nd: .472
3rd:  .578
4th:  .767
5th:  .805
6th:  .812

The more a hitter sees Justin Masterson, so far, the better he fares against him.  But this isn’t a normal increase in familiarity.  This is the hitter having real success off of a pitcher, too much success.

If this were the Nationals or the Royals, Justin Masterson would be a legitimate mid-rotation starter for a team that needs innings eaten.

His struggles against lefties, and in the later innings wouldn’t be enough to keep him out of the rotation, because there is no one else on those teams to fill those slots.  No one worthy of filling them anyway. 

But this is a team that might have seven capable starters in June or July.  And a guy named Michael Bowden in case of any real emergency. 

With all that depth, Masterson seems to be the best fit in the bullpen.  And if needed, he can always make a spot-start, or two.