The Dodgers have two outstanding young pitchers in Billingsley and Kershaw.  Even though they're now mainstays in the rotation, consider that Billingsley is 10 years younger than Kevin Brown was when he signed his $100,000,000 contract, and Kershaw is 13 years younger.  So for right now, I just want to look at Billingsley.  He's taken a bit of heat for not being as amazing as he was last year, but I want to know if that's warranted:

2008: 200.7 IP, 32 GS, 201 K, 80 BB, 2.51 K/BB, 14 HR, .248/.324/.363 against, 1.336 WHIP, 3.35 FIP, 3.14 ERA, 135 ERA+
2009: 178.7 IP, 29 GS, 159 K, 75 BB, 2.12 K/BB, 13 HR, .245/.326/.370 against, 1.304 WHIP, 3.62 FIP, 3.93 ERA, 106 ERA+

Based on the three true outcomes, it's not surprising to see a dropoff; he's got a slightly higher walk and home run rate in 2009, and a significantly lower K rate (8.0 vs 9.0 the previous season).  But it's equally strange how opponents have nearly identical batting lines against him.  Can 0.79 of ERA be explained by productive outs?  Or is it possible that Billingsley was a little bit lucky in 08 and a little bit unlucky in 09, but he's roughly the same good pitcher each year?

I do want to look at some pitch data that stuck out at Fangraphs:

Fastball
2008: 59.2% (91.5), -.06 wFB/C
2009: 51.1% (91.7), -.02 wFB/C

using his fastball significantly less means more breaking balls.  These could be more stressful on his arm (which would go nicely with the 6th inning struggles story).  This could also mean there might be a problem with some of his breaking balls.  Let's examine:

2008: 2.1% SL (85.4), 0.35 wSL/C, 18.8% CT (87.6), 1.96 wCT/C, 17.7% CB (77.8), 1.37 wCB/C, 2.4% CH (84.1), -0.96 wCH/C
2009: 4.1% SL (84.1), 3.47 wSL/C, 22.9% CT (88.9), 0.25 wCT/C, 21.5% CB (78.4), 1.57 wCB/C, 0.8% CH (85.7), -9.07 wCH/C

Billingsley improved every breaking pitch that he took a little velocity off, except for his curveball.  Given the velocity, I'm wondering if he actually abandoned his changeup and that's just the designation given to his slider when it doesn't work right.  And even if his fastball isn't his best pitch, it's probably not helpful to significantly back off of it.  Looking back at Baseball-Reference Splits for 2008 and 2009, his K/BB in 2 strike counts drops from 5.91 to 4.82 from 08 to 09.  Additionally, by counting the "after 0-1" and "after 1-0" PAs, Billingsley got first pitch strikes 55.6% of the time in 08 vs 54.3% in 09.  I'll hypothesize (but without looking at game data pitch by pitch won't say for sure) that relying less on his fastball has led more to Billingsley being slightly less dominant in 2 strike counts as well as slightly less able to come back from behind in the count.

Billingsley has been dinked around a bit more, and that seems like the biggest difference.  Despite even less playing time for Juan Pierre, Billingley has actually had more bases taken on him than previous seasons (34 thus far vs 22 all last season).  Further, he's had 11 sacrifice flies against him rather than 5 last season; while this is partly due to luck, not getting as many outs by strikeout does make a difference here; the sac flies alone account for 6 ER; Billingsley has so far this season a mere 8 more than last season.

Billingsley might need better advice about trusting his fastball to get ahead and stay ahead in counts, but otherwise, I don't see too much cause for alarm.