WATCH: Giants' second-half nightmare continues with walk-off loss to Rockies

The Giants had to turn to Joe Nathan to try to save the game

What is happening to the Giants right now is truly unbelievable. After posting baseball's best record in the first half (57-33), the Giants have baseball's worst record in the second half and it got even worse Wednesday night.

San Francisco took a 5-3 lead into the ninth inning against the Rockies, and closer Santiago Casilla immediately allowed a solo home run to Nolan Arenado. It happens. Arenado is awesome. A single (Tom Murphy) and a hit-by-pitch (Charlie Blackmon) followed, putting the winning run on base.

Manager Bruce Bochy had already replaced Casilla with lefty Josh Osich, and after the Blackmon hit-by-pitch, Bochy turned the game over to former All-Star closer Joe Nathan. That's how desperate things are for the Giants right now. Colorado eventually walked off on a Cristhian Adames double. To the video:

Boy, that's rough. The 6-5 walk-off loss (box score) on Wednesday was San Francisco's fifth loss in their its past seven games. The Giants are 17-32 in the second half. 17-32! Yikes.

At one point this season, the Giants were eight games up in the NL West. It wasn't even that long ago: June 26. Now the Giants are only a half-game up on a postseason spot. They sit in the first wild-card spot with the Cardinals and Mets tied for the second spot, a half-game back.