More photos » by Manuel Balce Ceneta - AP

Craig Stammen throws a two-seamer in his debut on May 21, 2009.

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Another week, another batch of debuts.  And another position player taking the mound (Ross Gload).  I'm only covering the "real" pitchers, as usual.  Minus Gload, that leaves these eight:

Craig Stammen
Promoted despite a paltry 3.2 K/9IP (gotta be the sub-2 ERA).  That's well off his 2008 total (7.6) and career minor league mark (6.7).  The Nationals gave Stammen a start this week, and it wasn't awful, nor pretty.  He worked into the 7th inning, allowed four runs on four hits (one home run) one walk and three strike outs.

Cristhian Martinez
A minor-league veteran, Martinez debuted for the Marlins with two innings of relief.  He allowed two runs, but struck out four batters.  He was optioned back down to Double-A the next day.

Clay Zavada
Signed by Arizona out of the Frontier League in 2008, the lefty jumped from Low-A to Double-AA for 2009.  He's got quite a story - it's in the New York Times.  He had been drafted by the Dbacks a few years earlier, but life had other plans.

Kris Medlen
Just 23, Medlen made an ugly start for Atlanta.  His rotation-mate in Triple-A Gwinnett is Tommy Hanson, and the two of them could be making a positive impact for the Braves sooner than later.

Dale Thayer
Another minor league veteran, Thayer worked a three inning save in his debut for the Rays.  He's averaged more than a strike out per inning in the minors.  Best known for his fledgling handlebar mustache.

Anthony Swarzak
In injury to Glen Perkins opened a spot in the Twins rotation for this 23-year old rookie.  Swarzak got the win in his debut on Saturday.

Sean West
The Marlins were busy with the debuts this week.  They had two of their own and hosted two others (Zayer and Zavada).  West, a 22-year old lefty, got the start Saturday night and did alright, all things considered.  Two runs in five innings, four walks and five strike outs for a no decision.

Carlos Fisher
Called up with Jonny Gomes, Fisher debuted in the 11th inning of an interleague game against Cleveland.  The Reds rookie was credited with the win when Alex Gonzalez connected for a walk-off double.

Read on for the PITCHf/x goodies.

PITCHf/x Profiles

Oddly enough, on the day of if the Indy 500, I found exactly 500 pitches from these new arms.

Click the table headers to sort.

Swarzak's slider, or slurve, is very nasty looking.  Thayer throws a hard two-seamer with lots of movement.  Those are really the two pitches that stand-out for me. 

West was the only pitcher to break 95 mph, which he did a handful of times, but didn't sustain the velocity, resulting in a lower average fastball speed than Fisher (who broker 94 once).  There's a mix of change-up/fastball separations in the group.  Anywhere from a 5 to 12 mph gap, approximately, amongst the eight rookies.

Like the sortable table?  OK, have another.  I've re-tagged events in my PITCHf/x database, so some things have changed.  rv100 is averaging slightly below 0, which was the case after the initial correction (that was a bigger one) and is still wrong.  nkSLG (total bases on all balls in play and home runs) is up from .51 to .52, the newer/higher being the more accurate (grand slams were not counted in the older version [!]). 

I've also added batted ball types, which helped me dig deeper and parse more events in the PITCHf/x data correctly.  Some error types are ambiguous (slightly) and there are a few goofy ones, but we're in better shape now than before.

Now, small-sample fun time...You'll notice pitch type is blank, that's because there are barely enough pitches to work with to begin with.

Swarzak's sinker was effective, but the slider wasn't.  Based on the teeny weeny samples, here were the most effective pitches by type (rv100) minimum 10 pitches:

• Change: Stammen (-3.4)
• Two-seam FB: Swarzak (-5.1)
• Four-seam FB: Thayer (-4.1)
• Slider: West (-5.7)

Medlen had the only curveball, by my classifcations, and the 15 he threw averaged out to an rv100 of 1.9.

Lastly, batted ball data, sortable, too.

Until next week....Happy Memorial Day.