The Rays stand at 20-7, and are owners of baseball's best record. They lead the American League in run differential, but that's only natural, considering they are first in runs scored and first in fewest runs allowed. While they might sustain the latter, with an excellent pitching staff and a terrific defense, their offensive performance is a bit more of a house of cards.
Despite leading MLB in run scoring to date, the Rays offense hasn't actually been all that great. They rank 10th in the league with a .337 wOBA, which is above average but not dramatically so. By comparison, the Yankees have a .365 wOBA, but have scored nine fewer runs. What gives?
Timely hitting. With the bases empty, the Rays are batting .227/.308/.373, and their .681 OPS in that situation ranks 19th in the league. With men on base, however, the Rays are at .306/.381/.490, second best in baseball. With runners in scoring position, they are hitting .319/.403/.524, again, second best in baseball.
The league average OPS goes up fifty points when a runner reaches base. The Rays OPS has gone up 190 points in those situations, and even further still when runners get to second or third. As such, they have a team Weighted Runs Created of 133 runs, or 27 runs fewer than they've actually scored.
This won't last, of course. No team can hit this well with men on base over a full season. If the Rays want to keep playing baseball at their current level, they're going to have to begin to start some rallies, rather than relying on getting so much production from the ones they're creating now.