Matt Bywater made his AA debut on Monday, pitching against the Harrisburg Senators. He was the Orioles 7th round pick in 2010 out of Pepperdine University. The lefty has a a sidearmed delivery, so I don't see how he is a starter. I hate to stereotype someone as soon as they throw their first pitch, but I can't really think of any sidearmed starters in the Majors (Bruce Chen probably counts, perhaps Paul Maholm as well, although his platoon splits have always been terrible). His career splits have been about what you would expect. He is pretty dominant against lefties (2.46 FIP, 2.51 SIERA), but mediocre to bad against righties (4.58 FIP, 4.32 SIERA). He threw a lots of changeups. They had decent downward movement and dip (it was a pitch he was more concerned about locating low the zone than throwing them in the dirt). He was missing a lot to his arm side.
It also looks like he has a low moving fastball. The pitch was hit pretty hard by righties, but could be a ground-ball pitch against lefties. He got some weak ground-ball swings from lefties. He has been a good ground-ball pitcher in the minors, with a ground-ball rate of 52.1% over the last two years. While I don't think he is a pitcher that will get a lot of swings and misses in the upper levels, his K% has been good over the last two years as well.
I could see him as a guy you bring in to throw a full inning when the lineup is lefty-righty-lefty and he can just throw all changeups to the righty in the middle. He threw mainly changes to righties, and threw quite a bit to lefties as well. He could also be a LOOGY or a AAA all-star, but I do think he would provide some relief value to a big league club in the future.
Jeff Locke made his first MLB start in 2012 on Monday against the Astros and wasn't bad (6/1 K/BB, 60% GB, 3.91 FIP). He started four (horrible) games for the Pirates last season and had pitched in 2 games as a reliever earlier this year. In AAA as a starter (24 starts), he was solid, with a 3.24 FIP.
Locke was pretty off-speed heavy (I won't use a lot of Pitch F/X since everything is so small sample size and I will be done with this post before the data from this game become available),especially to righties.
He has a curve at about 78-81 MPH (called a slider sometimes by Pitch F/X) that has some good bite. However, it has a tendency to stay up and turns into a batting practice pitch when it does.
His change is the pitch that scouts always liked about Locke and it sits at about 81-82 (averaged 81.4 MPH according to Fangraphs).The lefty's Fastball was only at 90 MPH (90.1 average) and was best when he threw it down. I think he has the tools to get right-handers out enough to be a starter, but he certainly won't be a dominating one. If he turns out to be a league average starter, I would be mildly surprised and the Pirates should be thrilled.