Colorado Rockies: Which teams are the biggest Wild Card challengers?

Atlanta Braves, St. Louis Cardinals, Pittsburgh Pirates
These teams are being bunched together, because they aren’t an immediate threat. They are teams that fans should check up on every now and again. Who knows, maybe one of them can start making a run and become a contender for that last wild card spot.
The Braves are seven games out of the wild card. They are sixth in the league for batting average, but 20th in ERA. Atlanta is another team that could go either way with the trade deadline, especially since they have no chance of catching the Nationals in the NL East.
The Cardinals are seven and a half games out of the wild card. St. Louis is the opposite of the Braves. They are sixth in ERA, but only 20th in batting average. The Cardinals should be buyers for this trade deadline, because the NL Central is such a close race. Which makes an historic team like the Cardinals, a team to be worrying about.
The Pirates are 8 games back of the wild card. Their pitching is average, but their hitting is below league average at .244. Again, since they are a part of the NL Central, I wouldn’t be surprised if they were buyers in the upcoming trade deadline, which would make them more competitive.
Next: Could Tyler Chatwood's injury impact Colorado's deadline plans?
The Rockies are sitting relatively comfortable, given the fact they have gone 7-15 since June 21, when they fell out of first place in the NL West. The Rockies must continue to play well if they want to make it to their first playoff appearance since 2009, especially since they have solid competition only a few games behind them.