This is my first FanPost here at AA, I've mainly been a lurker, so if there is anything painfully obvious I am missing or this has already been covered, I hope someone will tell me so I don't look like a jackass :). 

The Mets rotation hasn't exactly been their strong suit this year.  Mets' starters have a cumulative 4.61 tERA* (tRA scaled to ERA instead of RA) and a 4.42 FIP.  Once you get past Santana, Livan and Plefrey, you have a bunch of replacement level scrubs who really have no place on a major league team. 

I'm talking specifically about Oliver Perez (who Minaya thought was somehow worth 36 million), Tim Redding and Fernando Nieve.  This year, those pitchers have a combined 5.26 FIP; which would be fine coming from an inexperienced prospect with potential, but none of those players fit that description.  Nieve is the youngest of the trio, and he is 26 and hasn't been a starter in the majors in 3 years partially due to injury; although his career 4.23 minor league FIP suggests he was never that much of a prospect to begin with.  Anyway, the point is that none of these guys have much potential and are likely pitching as well as they ever will.   

That brings us back to Niese.  If you are going to be giving half of your starts to replacement level pitchers, why not at least give some of them to a youngster with some potential to improve on that in the near future?  With the Mets not exactly swimming in starting pitching prospects, 23 year old Jon Neise rises to the top.

According to minorleaguesplits.com, he has a career 3.68 FIP in the minors (along with a solid 52.1% ground ball rate), and it has been a combined 3.61 in AAA over the past 2 years.  In limited time in the majors, he has a 3.66 FIP.  ZIPS projects him to have a 4.39 FIP this year which is almost exactly average.  

Given that the guys he would replace would likely be replacement level, he would be expected to add about 1 win in the second half of the season if he pitches 100 innings.  That 1 marginal win, could be pretty damn important to the Mets.  Over the past 2 years, they have missed out on the playoffs by exactly a win, and the division looks to be very tightly packed again this year.  Of course none of that is even considering that Niese is a legitimate prospect, and it would probably be beneficial to give him more playing time in the majors.

So with that all in mind, let's take a look at Niese's stuff as a pitcher using Pitchfx.  Unfortunately, Niese has only pitched 24.2 innings in the majors and there is no Pitchfx data in the minors... so our sample size will be small.  Still it would be nice to see how his stuff looks and even the small amount of data should allow us to make reasonable assumptions as to his stuff right now.  As far as I can tell, he has thrown 3 distinct pitches; a fastball, a curveball and a changeup.  Here they are, mapped out in flight path form:

If it's a little fuzzy, you can click on it for a larger view.

That graph is pretty self explanatory.  It basically shows the movement paths of all of his pitches, or at least a pretty good guess based on various data from gameday.

Of course you can make any conclusions you want using this graph, but as you can see, he has almost no horizontal movement on his pitches.  His fastball/combo looks decent, as the two pitches start off on the same plane and then the changeup has some decent drop to it; however, the speed differential isn't great.  His curve is a real yacker, with an enormous "hump" to it and over 11 inches of vertical movement.  He also throws it from a different release point.  That combined with the giant hump means it should be easily detectable early in the path, meaning it likely won't be a power pitch for him in the majors, but as Dave Allen noted at FanGraphs, the fact that it has so much movement *should* make it a plus pitch.  Overall, he has pretty standard stuff for a lefty, maybe a bit above average.

I could show you his pitch location graph, but given the small sample size it wouldn't be very representative.  Going by his career walk rate in the minors ( about 3.0 per 9), that one time I actually saw him pitch :), I would say his control is currently about average, maybe a bit below.

Conclusion:

Niese has put up good numbers in the minors, and is only 23 years old and likely with room for improvement.  In limited time in the majors, he has demonstrated roughly average stuff and has good results overall.  He is projected to be almost exactly a league average pitcher this year.  I say, bring him up!  He would almost certainly represent an upgrade over the current 4/5 starters on the Mets which given their placement on the playoff odds scale could be huge; and unlike them, he might actually contribute to the team in future seasons.