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Jered Weaver turned in one of his best starts of the season Wednesday night, holding the White Sox scoreless for six innings. He also struck out five batters, which wouldn't be a big deal for most starters. For Weaver, it was matching a feat he had accomplished only four times in his prior 17 starts.
Could there be more where that come from?
Wednesday's start bumped Weaver's strikeout per plate appearance ratio (K%) up to 13.5 percent, which would be the fifth-lowest among starters, if he qualified. It's easy to dismiss Weaver as a source of strikeouts given his mid-80s "heater," but forecasting his future strikeout potential isn't so straightforward. Swinging strike percentage (or whiff rate) is a good predictor of a pitcher's K%, and Weaver has induced whiffs on 9.6 percent of his pitches. For a typical pitcher, that would result in 17.8 K%, which is close to major league-average and the same as the rate achieved by Jeff Locke and slightly higher than those of Jeff Samardzija and John Lackey. If Weaver performed like other pitchers with a similar whiff rate, he would still not be a strikeout pitcher, but he'd be much closer to being one.
The 4.3 percentage point deficit between Weaver's actual K% and the K% we would expect given his current whiff, called strike and foul rates is the largest of any pitcher with at least 100 innings pitched this season. Weaver has the lowest foul ball-to-strikes thrown ratio in the majors, and logic would suggest that the lack of strikes-by-foul might be depressing his K%. Then again, foul rate is not nearly as strong of a predictor of K% as whiff rate is, and Tyson Ross, Francisco Liriano and Chris Heston haven't seen their K% eroded by a similar lack of fouls hit against them.
Weaver is already on something of an upward strikeout trajectory, as his 15 Ks in three August starts already top his monthly totals from April (five starts) and June (four starts). Even without that trend, Weaver's respectable whiff rate suggests that he could be a decent strikeout pitcher going forward. He is currently starting in only 34 percent of the leagues on CBSSports.com, so it may be time to dust Weaver off and get him in your rotation in mixed leagues with more than 12 teams.
Here are five other starters who have been K% outliers as compared to their expected K%.
Rubby De La Rosa, SP, Diamondbacks: When it comes to getting swings-and-misses, De La Rosa has been in a class with Zack Greinke, Masahiro Tanaka and Matt Harvey. While each of his cohorts has a K% in excess of 23.0 and a K/9 ratio above 8.0, De La Rosa's 12.6 percent whiff rate has translated into a 19.0 K% and 7.2 K/9. Instead of having the strikeout numbers of a must-start Fantasy option, he has across-the-board stats (including strikeout rates) that resemble those of teammate Jeremy Hellickson.
De La Rosa's 15.5 percent called strike rate, which pales in comparison to the major league norm of 17.6 percent, is what is preventing him from reaching the Greinke/Tanaka/Harvey tier of strikeout pitchers. His mediocre control and penchant for allowing homers will keep him well below their level in terms of Fantasy value, even if he gets a late-season bump in his K-rate. Hector Santiago provides a better comparison, but because the Angels' lefty has overachieved due to an 82 percent strand rate, his 4.10 FIP is probably a better indication of what his ERA -- and De La Rosa's -- will be going forward than his actual 2.86 mark.
In other words, a bump in strikeouts would enhance De La Rosa's value, but not by all that much. Owners can treat him in the same way that has worked up to this point, sitting him against lefty-laden lineups and starting him against righty-heavy offenses.
Erasmo Ramirez, SP, Rays: Like De La Rosa, Ramirez has a whiff rate on the north side of 12 percent (12.1 percent, to be exact), a below-average called strike rate (16.2 percent) and middling strikeout rates (18.4 K%, 6.8 K/9). That is where the similarities end. After staying on a torrid whiff pace over the season's first three months, Ramirez has cooled off since early July, posting a 9.1 whiff rate that would be even lower if not for a 15-whiff performance against the Red Sox on July 31. Of late, he has been less of a whiff-inducer than De La Rosa, but at least he isn't burdened by lopsided lefty-righty splits.
If Ramirez can re-establish his swing-and-miss tendencies, particularly with his slider, he could emerge as a strikeout-per-inning threat. However, since we haven't seen Ramirez miss bats consistently in nearly two months, the safer play is to expect a more modest level of production. In fact, he could be roughly as productive in Fantasy as he has been all along, as his strikeout rate could rise slightly, but he will most likely see an increase in his .254 BABIP and 1.09 WHIP.
Lance Lynn, SP, Cardinals: No pitcher with more than 100 innings has a bigger positive gap between his actual K% and his expected K% than Lynn, and no one else is close. His 24.8 K% is the 16th-highest among qualifying starters (and his 9.6 K/9 ranks 11th), yet his 10.8 percent whiff rate ranks outside the top 30. Even with an otherworldly 19.9 percent foul rate, Lynn's expected K% is 19.7, or just 0.2 percentage points higher than CC Sabathia's.
For three seasons running, Lynn has been below average in getting called strikes, so he needs an especially high whiff rate to stay at or above a strikeout per inning. He could be just an average strikeout pitcher the rest of the way. If he somehow manages to keep his current pace, Lynn could wind up being overvalued in drafts next season, and he would almost surely earn a place on my annual busts list.
Nathan Karns, SP, Rays: Only two qualifying starters have a BB/9 above 3.3 and a HR/9 above 1.1 -- Karns and Trevor Bauer. While Karns is neither as wild or as homer-prone as Bauer, he also doesn't match his Indians' counterpart in whiff rate. Karns falls well short of Bauer in that regard, putting up a pedestrian 9.4 percent whiff rate as compared to Bauer's 10.7 percent rate. We have seen how far strikeouts have taken Bauer in the absence of control and homer-prevention -- that is, not far at all, given his 54th-place ranking among starting pitchers in Fantasy points.
Karns, who has scored 11.5 more Fantasy points than Bauer, could find himself in free fall if his 23.4 K% and 8.8 K/9 predictably regress. He is dependent on strikeouts for his Fantasy value, and his current pace looks highly unsustainable.
Mike Fiers, SP, Astros: Judging by his merely decent 9.9 whiff rate, Fiers' days as a strikeout-per-inning pitcher would seem to be numbered. Then again, his 9.1 K/9 from this season matches his career mark, and his 23.4 K% is actually a tad below his career 24.1 K%. Fiers' act is a tried and true one. With a low 90s fastball and near-average whiff rates, Fiers doesn't profile as a strikeout pitcher, yet he has been consistently well above average.
A high called strike rate has been key to Fiers' steady strikeout pace, and this season, it has actually been unusually low at 15.7 percent. However, he has compensated for it with a 20.7 percent foul rate. While that latter mark could easily regress towards a normal rate, he could continue his recent upward trend in his called strike rate. Given his history of piling up strikeouts in the face of mild whiff rates, there is little reason to worry about Fiers' K-rate falling.
That doesn't mean Fiers won't see a dip in the pace of his strikeout total, but the risk is due to a potential loss of innings with Lance McCullers rejoining the Astros' rotation this weekend. According to the Houston Chronicle, Fiers isn't slated for bullpen duty, but he could have some of his turns skipped.