It began with a 15-3 win over the Tigers on June 9. The Sox had 16 hits, including 3 HRs. They beat Detroit again the next day to take two out of three. In the last 30 games, the Sox have outscored their opponents 156-77. That gives them a Pythagorean winning pct of .804. In 30 games that would be 24.1 wins. All data is from Baseball Reference.
The Sox hitters have a .793 OPS in these games. The following formula shows the relationship between runs per game and OPS from 2001-04 (may not be the most accurate formula for this case, but I had it handy).
R/G = 13.27*OPS - 5.29
It predicts the Sox would score 5.22 runs per game. That is very close to what they have actually done (5.2). The Sox pitchers have allowed an OPS of .626. That would work out to about 3 runs per game or 90 total runs. They have actually only allowed 77.
The Sox OPS differential is .167. The next formula shows the relationship between OPS differential and winning pct.
Pct = 1.26*OPSDIFF + .5
This gives the Sox a pct of about .710. That would be only about 21 wins (which would still be very good). The big thing is that the Sox pitchers are allowing fewer runs than expected based on the OPS they have allowed. They must be doing well with runners on base in the last 30 games (but for the year they have allowed a .704 OPS overall while it is .741 with runners on). The Sox have out homered their opponents 34-17.
They have won or swept 9 of their last 10 series. The only series they lost was 2 out of 3 to the Royals a couple of weeks ago in KC. They avenged that with a 3 game sweep in Chicago, outscoring them 28-8. They beat the Tigers 2 out of 3 to start this run when the Tigers were in 2nd place. But the Tigers were recently in first place until yesterday. The Sox also swept the first place Braves and took 2 of 3 from the Rangers. And last week they swept the 2nd place Angels 4 straight in Chicago, outscoring them 19-5. In the five losses, the Sox have not lost by more than 2 runs, losing all 5 by a total of 9 runs.
Now if we can only get Oswalt from the Astros to take Peavy's place.