Bronson Arroyo has thrown over 200 innings in every season since 2005. Last season was the first in that stretch where he yielded less than 200 hits. Most of his success comes against right-handed batters, and he has done well pitching them away.
Arroyo was very efficient with his pitches to the outside corner. The above graphic shows all his pitches that would qualify as hitting the outside part of the zone in 2010. Last year, 43.6% of those pitches were curveballs, the highest of any pitcher throwing outside to righties. Batters struck out 30.8% of the time and produced an overall wOBA of .130 against curves in that zone (298 pitches, 91 PA). In his career, Arroyo has a 31.2% K-rate on curves to RHB in that zone with a wOBA of .171 (890 pitches, 261 PA).
With two strikes versus RHB last season, Arroyo went to his curveball 38% of the time, most of any pitch in his arsenal. Batters swung 63.4% of the time and struck out 43.2%. When they did make contact, the result was a miniscule .062 batting average and .148 slugging percentage. At this point in his career, opposing batters are probably well aware of what's coming - but Arroyo continues to make that pitch work.