On Saturday, I looked at three starting pitchers with the potential to experience a K/9 surge in 2012. Today I will use the same methodology of comparing the pitcher’s SwStk% to his K/9 to look for those who may see a K/9 decline next season.

Bartolo Colon | 5.4% SwStk% | 7.5 K/9

Among qualified starters, Colon’s SwStk% is the second lowest in baseball. His 7.5 K/9 is the highest mark he has achieved since all the way back in 2001, yet his SwStk% is actually at the lowest mark of any year FanGraphs has data for, starting in 2002. So how is he punching out batters at a much higher rate than his SwStk% would suggest? His called strike percentage is at 22.9%, well above the MLB average for starters of 18%. That actually leads all of baseball. Though he has typically been above the league average in that department, this is a career best called strike percentage. I highly doubt this is sustainable, and his strikeout rate will likely tumble next year. Since his control remains good and he has induced more grounders this year (though whether this is sustainable is anyone’s guess), he may still be relevant in AL-Only leagues, but should have no mixed league value.

Tim Stauffer | 6.5% SwStk% | 6.2 K/9

Stauffer has displayed a solid mix of skills, possessing good control, decent strikeout ability and an excellent ground ball rate. All in all, his ERA matches his SIERA and xFIP almost identically. But that strikeout rate may not last, unfortunately. Although his K/9 isn’t as high as Colon and doesn’t have as far to fall, it is tough to figure out what exactly is supporting the mark. His called strike percentage is just a bit above the league average, so you cannot point to that. Given his history, it is just as probable that his SwStk% does rebound next season, keeping his K/9 stagnant. But if it doesn’t, then his K/9 will drop into the mid-5.0 range, which will really limit his fantasy value.

Ryan Vogelsong | 7.2% SwStk% | 7.0 K/9

Vogelsong is one of the top candidates for surprise of the season, but he has not imploded like most probably thought he would after his great start. However, regression is certainly in full effect, as his monthly ERAs have risen every single month. Vogelsong’s career SwStk% is 7.5%, a tick above what he has posted this year, yet his career K/9 is at 6.5, below this season’s mark. Called strikes have helped him, as he ranks eighth in baseball in the category. Even in past seasons he has usually been above average in the category. That may mean his K/9 won’t go into free fall, but next year it is likely it drops into the low 6.0 range, rather than tough 7.0. Any drop in strikeout rate could quickly make Vogelsong worthless in mixed leagues after accounting for expected regression from luck factors.