In every statistic you would want a young pitcher to improve upon, Arrieta has done so. Strikeout rate? He's striking out 8.07 batters per nine innings after striking out 5.94/9 in his first two seasons. Walk rate? He's slashed his walk rate from 4.39 BB/9 in his first two seasons to 2.49 BB/9 this season. As a result, his FIP has gone from 5.08 in his first two seasons to 3.88 this year.
As long as Arrieta continues to pitch as he has this season -- the same way that's gotten him a 3.88 FIP and 3.65 xFIP -- he may just become a consistent, #3 starter that the Orioles desperately need behind Jason Hammel and Wei-Yin Chen.
A heavily debated topic on this forum.