1. The ball; it seems to be effecting fly balls more which is hurting runs scored. There really isn't a huge difference between this April and last year when it comes to swStr% or contact %. It's definitely slightly down, by around .4%, but it's not dramatic.
2. Velocity. I thought pitchers would benefit from the shortened season last year and so far they may have. Time will tell. Every tick in velo is going to be a slight tick up in k rate and a tick down in contact %. Velo is likely up a bit because of the continued rise of the reliever.
3. Bullpens and IP/start. The trend continues as fewer starters are ever able to see a lineup 3 times. I find it fascinating that offense is WAY down, meaning pitching has been good, but the avg starter is barely over 5 IP/start. This means that despite good performances, arms are just getting the hook.