Rating the rotations: Cards, White Sox best

The Cincinnati Reds should be glad that they’re retooling their rotation as they approach the quarter-season mark, because thus far its been the worst in the National League, per Baseball Prospectus’ Support-Neutral Winning Percentage, or SNWP.

SNWP measures how far above or below a club’s starting pitcher is propelling their club -- not themselves -- toward notching a win in an individual ballgame. This is truly "support-neutral," in that it measures performance without any consideration of the things that are beyond a starting pitcher's control, like the run support he receives, or the quality of the defense behind him. Add up the SNWP for a rotation collectively, and you can evaluate how strong a team’s rotation is, top to bottom.

The idea is straightforward enough: Everyone starts out at .500 with all other things being equal, as this is even park-adjusted. The metric simply looks at how much starting pitchers are contributing toward a team’s final results via their pitching, moving the dial above -- or below -- that .500 record.

The leaders from the early going so far this year won’t surprise you. The Cardinals and Phillies are the class of the senior circuit, while the White Sox are riding high in the AL with a .542 mark -- and that's getting achieved with very little help from Jake Peavy. Taken from Baseball Prospectus’ sortable stats page, here’s where everyone ranks through Wednesday’s action:

The Reds’ SNWP is a league-worst .465, placing them in a virtual tie with the Blue Jays (.464), and only clearly ahead of the Orioles (.454). As Jim Bowden gets into in greater depth today, absences are part of the explanation, as well as a big part of the expectation that things will get better.

However, even with Johnny Cueto and Homer Bailey back in action, the surprising fact is that this year’s work with Sam LeCure and Mike Leake in the front five most of the time didn’t deliver a much worse mark than Cincinnati’s 2010 performance, when it was 14th in the National League with a .477 SNWP -- and the Reds won the division anyway. Then as now, the Reds had to patch up their front five in-season, with Travis Wood getting called up to stay during the summer, and Edinson Volquez coming back from Tommy John surgery and a PED suspension.

The question with the Reds is less about their performance than their perceived promise. Everyone expects better from Volquez, but with just one quality start in eight turns, plus a league-leading 32 unintentional walks allowed in just 42 1/3 IP, there’s a fairly large gap between expectations and execution. The challenge is for Dusty Baker and pitching coach Bryan Price to convert long-anticipated promise into production.

Looking around at the rest of the majors, the Indians and Royals have already gotten plenty of media play for their surprising early-season performance. Cleveland is getting the benefit of four horses consistently delivering winnable games now that Carlos Carrasco (.496) is back in action; while no single pitcher is dominating (Fausto Carmona's .521 leads the team), the Indians already received 26 quality starts in 36 games.

The teams especially interesting to find among the initial successes are the Nationals and Pirates. The Pirates are getting some benefit of seeing Charlie Morton finally live up to his billing as a prospect with the Braves, and journeyman Kevin Correia was one of the better bounceback bets on the market last winter -- give Neal Huntington some credit. Not that anyone is going to award Mike Rizzo an executive of the year award just yet either, but the value the Nats are getting from a healthy Jason Marquis and the indestructible Livan Hernandez has helped take the pressure off Jordan Zimmermann and John Lannan while keeping a team stuck with the league’s worst OBP on offense around .500. Marquis has six quality starts in seven turns, providing some reassurance that his big first-half streak of 2009 with the Rockies wasn’t a one-time thing.

If this does wind up being another year of the pitcher, there are going to be plenty of mound turnarounds to tout -- evaluating how significant they are relative to the team’s winning, however, is where relying on a signpost like SNWP should prove helpful.

Christina Kahrl covers baseball for ESPN.com. You can follow her on Twitter.