The Brewers 3.49 ERA over the last four months of the season is first in the NL. The Mets (3.93, 7th in NL) and especially the Diamondbacks (4.69 ERA, 13th in the NL) have been considerably worse.
I'm seeing SDP at 64 W - 42 L with the best winning percentage in the NL over the last four months, though ARI (64 W - 43 L), NYM (64 W - 44 L) are right behind them before MIL (61 W - 47 L) shows up.
The two best teams - LAD (60 W - 45 L) and PHI (58 W - 48 L) - have been the worst teams among the likely NL playoff clubs over the last four months.
It's about as wide open as its ever been.