The White Sox OPS in high-medium-low leverage situations .874-.642-.654 Their pitchers allow .510-.629-.673. Thru yesterday. So a bit luck.
They had a team OPS of .688 and allowed .622 for a differential of .066. Using all teams from 2010-14, the relationship between OPS differential and winning pct is
Pct = .5 + 1.3246*OPSDIFF
That estimates the Sox to have a .587 pct (much lower than their actual of .680 thru yesterday). In 25 games, that is about 14.7 wins or 2.3 fewer than they actually have (they may have increased their OPS differential with today's game).
.587 is not bad, but it is far below .680.
Using the same years, here is the equation when breaking things down by leverage
Pct = .5 + .306*LOW +.420*MED + .564*HIGH
Estimating the Sox pct here would be
Pct = .5 + .306*(-.0058) + .420*(.013) + .564*(.364) = .705
That is a bit high, but much closer to .680 than .587. It estimates the Sox win total to be 17.6. That is only off by .6 wins, much less than the 2.3 from using overall OPSDIFF. That differential in high situations is probably not going to last very long. From 1960-2014, the biggest differential in high leverage situations belongs to the 1995 Indians, with .208.
The lowest OPS allowed in high leverage situations was .552 by the 1965 Dodgers. The Sox .854 OPS by their hitters would rank tied for 25th out of 1,432 teams. So they have been incredible both ways in high leverage situations.