The Oakland Athletics have been on a dominant run since they had some key players return from injury. 31-13 is a stretch of baseball that will get you into the mix quickly regardless of your previous record, as Oakland is showing. Let's see the main reason for their sudden offensive surge, using Net Runs Above Average.
Crosby has been a monster since returning from the disabled list. That NRAA of 27.10 is pretty impressive, and when taken into the context of his position is even greater. With the addition of Dan Johnson to the lineup as well (.275/.356/.449 in 42 G) filling in for the injured Erubiel Durazo, as well as Eric Chavez's return to form, the A's offense went from anemic to dangerous seemingly overnight (although I'm sure it seemed longer to A's fans watching the struggles). Let's take a look at Chavez's monthly splits to see just how severe his issues were.
As you can see by the graph, in June Chavez exploded. He's returned to earth somewhat in July, but is still roughly 100 points of AVG/OBP/SLG over where he was in April, and besting his May performance as well.
As for the pitching staff, it has had essentially no problems since Rich Harden returned. Danny Haren is as good if not better than Mulder 2004 (and 2005 as well) and Rich Harden is the best pitcher this team has had in awhile, potentially and most likely already better than the best of Zito/Hudson/Mulder. Barry Zito though is actually not that much better peripheral wise than previously in some respects:
We can see here 2003 is really the year it all started to fall apart, but since his ERA stayed at a pretty good level no one really noticed too much. One thing that strikes me about Zito; he seems to have some control over BABIP, as evidenced by all of his seasons under the league average (many of them well below). His career BABIP is .274; league average for that period hovered between .300 and .310 to give a rough estimate. Zito is a pitcher with a high homerun rate and low hit rate (excepting 2004). If he is indeed a pitcher who has the rare ability to control hits on balls in play it would explain his performance. From a different, non statistical point of view, Peter Gammons says that his velocity is back to where it was during his Cy Young campaign of 2002, which would also explain the difference. Of course, almost 60 points lopped off of your BABIP is going to help too. Looks like Zito might be back though, as long as he can keep those peripherals where they are (or better of course).
Overall, the A's look like a dangerous team, especially with Huston Street now in the closer's role rather than the ineffective and inconsistent Octavio Dotel. Justin Duchscherer and Huston Street rank 13th and 20th in the American League in WXRL, which is:
If your wondering, Octavio Dotel ranks 88th. Adding Joe Kennedy to the pitching staff has also helped; he has already warmed the hearts of some A's fans with his shutout performance in extra innings a few games back. Just wait until Dan Meyer is ready to make it to the majors again after fully recovering from his injuries. This is an A's team built to last, and I think we might not hear much from the anti-Beane crowd in season for awhile now. My favorite kind of silence in the media is the kind a successful Beane team can create.