The Washington Nationals acquired Blake Treinen from the Oakland Athletics as part of the deal that sent Michael Morse to the Mariners and John Jaso to the A's. Treinen was a 7th round pick out of South Dakota State in 2011 (a year after being a 23rd round pick by the Florida Marlins) by the A's
In 2012, he spent the entire year in the California League as a 24 year old in which league average age was 23.2 for pitchers and 22.5 for hitters. He threw 103 innings, mostly as a starter with a 3.43 SIERA, 3.55 kwERA, and 95 FIP - (using both league and one year park factor). Of course, common prospect wisdom tells us (if not to just ignore minor league, especially pitchers, numbers altogether) that numbers put up by pitchers too old for a league mean nothing really.
To test this, I looked at pitchers that were too old (at least 1 full year above league average) for their league in the Cal League from 2005-2009 (giving them time to reach the Majors or fail). For ones that made the Majors, I put the average Cal League FIP - from that year in the parenthesis. I also added their average velocity as another informative variable.
2009 Cal League:
2 out of 38 (77 FIP -), 90.4 MPH
2008: 2 out of 23 (98 FIP -) 91.2 MPH
2007: 4 out of 38 (77 FIP -), 90.4 MPH
2006: 2 out of 27 (88 FIP -), 89.55 MPH
2005: 7 out of 41 (76 FIP -), 88.62 MPH
So it seems that the older pitchers that made the Majors were better than Treinen was in A+ statistically, but they didn't throw very hard. They could have been old for the level because the teams didn't believe in the pitchers because they threw so soft but overwhelming numbers somewhat forced them to give them a look. Just from a cursory look, they didn't appear to be very good in the Majors (which is expected because of the velocity), but I didn't factor that in.
Now what about 25 year olds in AA, since that is what Treinen will be next year (I am assuming)? Since he will be pitching in the Eastern League for the Nationals organization, I looked there from 2006-2009 (giving the players plenty of time to sort out their careers). Since there were a large number of them older than 24, I only included 25-26 year olds and this time, I looked at how they did it in the Majors.
2009: 6 out of 26 made the Majors with a total of -1.5 WAA. Average FB of 91.15
2008: 11 out of 27 made the MLB and had a -5.5 WAA with Average FB of 90.04
2007: 12 out of 32 made the MLB and had a -6 WAA with Average FB of 89.32
2006: 4 out of 24 made the MLB and had a -2.3 WAA with Average FB of 88.15
Almost without exception, these pitchers were unsuccessful in the big leagues and had weak to slightly below average fastballs (it is interesting that it went up every year). So what about Treinen? He doesn't seem to fit fully in this group, as he has hit 95 MPH on his fastball. So one the one hand, he wasn't as dominant for his league despite his advanced age as we have seen other older pitchers that ended up making the big leagues. However, he throws harder, and we know fastball velocity is more important than minor league statistics. So I went back and watched Treinen on MiLB.TV. His delivery reminds me of Scott Patterson somewhat as a really tall pitcher with a noisy delivery that seems really jerky (this seems to be a reason why most view Treinen as a reliever long term). The comparisons stop there though as Treinen's fastball is better (he was around 93 MPH on June 26th) and he has a high leg kick, unlike Patterson. He seems to get some decent sink as well
He is said to have a cutter, but it looked like his moving fastball as it moved more arm side than glove side (which is what you would expect a cutter to do).
He also reportedly throws a curve, but it must not be a big part of his repertoire, as I didn't see it, which is a big difference between him and Patterson obviously.
His change fades arm side and he seemed to have problems getting it down. He seemed to throw it a lot, but I would expect him to ditch it if he ever goes to the bullpen. If he goes there, I expect him to be a guy who throws hard, hard, and harder. In the rotation, I don't really expect him to miss many bats, and instead having to rely on command and ground-balls.