It's no secret that Derek Lowe has struggled during the past 2+ months of this season after a pretty good start to the year.  His first 11 starts can be categorized for the most part as strong outings, while his last 13 starts, not so much. 

In his first 11 starts, Derek Lowe pitched 63.2 innings, allowing 25 earned runs and recording 56 strikeouts for an ERA of 3.53 and a K/9 of 7.92.  Lowe held opponents to .238/.304/.358 slash line with a BABIP of .287, which is near average for pitchers.

In contrast, over his last 13 starts, Lowe has gone 69.2 innings, allowing 47 earned runs while only punching out 36 batters for an ERA of 6.07 and a K/9 of 4.65.  Opponents during this time are hitting .313/.374/.417 with a BABIP of .348.

Over these 2 "halves" of Lowe's season to this point, his ERA has jumped 2.5 runs while his strikeout rate has plummeted by nearly 3.5 per 9 innings.  What has caused such a dramatic shift in Lowe's numbers? Watching his past few starts, it seemed to me that Lowe had quit throwing his slider, which was the key for him during his stretch run last September, and earlier this year. 

Gameday from MLB.com allows you to go back and look at the breakdown of the pitch selection Lowe used during each start, and I compiled these to look for some trends. 

First 11 Starts: Sinker- 499   Slider- 307   Changeup- 163   Cutter- 133     Total=1102 pitches

Last 13 Starts: Sinker- 597   Slider- 279   Changeup- 190   Cutter- 89        Total=1155 pitches

Pitch % First 11: Sinker-45.28   Slider-27.86   Changeup-14.79   Cutter-12.07

Pitch % Last 13: Sinker-51.69   Slider-24.16   Changeup-16.45   Cutter-7.7

Lowe is relying more heavily on his sinker throwing it almost 6.5% more over his last 13 starts.  He's throwing his changeup slightly more while not using his slider or cutter as much as he did during his first 11 starts, about 4% less each.

Lowe threw 27 or more sliders in 8 of his first 11 games, and also 10 or more cutters in 8 of his first 11.

In his last 13, he has thrown 27+ sliders in only 3 of 13 games, while throwing 10+ cutters in only 4 of 13 starts.

For whatever reason, Lowe has gone away from using his slider and cutter, and like many pitchers that don't mix their pitches well, he's now getting lit up.  Lowe needs to get back to throwing his slider and cutter if he wants to regain his form from earlier this year.