The Wall Street Journal had an article yesterday called "Going to the Middleman" By ALLEN ST. JOHN. It is at
http://online.wsj.com/article/SB119335329621572171.html?mod=at_leisure_main_reviews_days_only
He shows how the Red Sox have an OPS differential of .153 in the 7th and 8th innings this past season while the Rockies only have .089. That is, the Red Sox had an OPS .153 better than their opponents and the Rockies were .089 better. The edge for Boston is .064. But in all innings the Red Sox had an OPS differential of .101 while the Rockies had .038. That means the Red Sox had an edge of .063 overall. So their edge in the 7th and 8th innings is no more than their edge any other time.
Certainly each team probably benefited by having such a big differential in the late innings, but it confers no special advantage for the Red Sox over the Rockies right now.
The big source of the advantage for each team is their pitching. The Red Sox hitting OPS in those innings is just .010 higher than it is overall and the Rockies is actually .005 lower. The Red Sox OPS allowed is .042 lower than overall and for the Rockies it is .056.
The Red Sox had an overall hitting OPS of .806 this year while it was .816 in the 7th and 8th innings. They allowed a .705 OPS overall and allowed .663 in the late innings. For the Rockies hitting, it was .791 and .786. For their OPS allowed it was .753 and .697.