"That pitch -- thank God for 'Welly' for winning that ballgame because I was not going to be able to live with that one," Hendricks said. "I think [the count] was 2-2 [to Holliday], and I was trying to pitch around him. If I walk him, I walk him. I know that, that's my mindset, and we talked about that in the [pregame] meeting.
"I throw a sinker, it starts on the black and cuts -- it didn't sink. I went back and watched it on video, and I still can't believe it ended up where it did. You just have to move on, and thank God we won."
The ball ended up in the left-field bleachers to cap a three-run St. Louis sixth. Hendricks was lifted after that.
"He threw the ball really good, and only one mistake with Holliday, and that tied the game," Castillo said. "It was supposed to be a two-seam down and in, and it was straight down the middle. I know he doesn't want to make that pitch, but sometimes stuff happens."
St. Louis' Pat Neshek must feel the same way. With the game tied at 3 and one out in the 10th, Anthony Rizzo doubled off Neshek, lining the ball to the right-center gap, with the ball bouncing into the ivy. Rizzo -- who had three hits to set a career high at 144 this season -- moved up on Jorge Soler's groundout, and Luis Valbuena was intentionally walked for the second time in the game to set up Castillo, who lined the ball into right for the game-winner.
"The second time [Valbuena was walked], I was ready for it," Castillo said. "I was on the bench thinking about the situation [in the 10th]. ... I was really ready for it and prepared.
"I was aggressive, looking for something over home plate that I can drive, and he threw me a slider over home plate and I was on it, I was on top of that and I was lucky to hit it."
It was the Cubs' seventh walk-off win this season and first since Rizzo homered Sept. 15 against the Reds. St. Louis manager Mike Matheny felt Neshek was just who they needed in that situation.
"Rizzo got a hold of one pretty well and then it got to a point where we had an opportunity to get around a left-handed batter and put a righty in front of [Neshek]," Matheny said. "Castillo just ended up putting together a good at-bat."
With the loss, the Cardinals have a 1 1/2-game lead in the National League Central over the Pirates, who clinched a postseason berth with a win Tuesday night over the Braves. St. Louis' magic number for winning the division remained at four.
Valbuena was unintentionally walked to open the Chicago second, and Castillo followed with his 13th home run off a 2-2 pitch from Cardinals starter Shelby Miller. Rookie Matt Szczur made it 3-0 with a leadoff home run in the fifth, his second big league blast and first at Wrigley Field.
With the win, the Cubs are 40-40 at Wrigley Field with one home game remaining on Wednesday.
"Everybody thrives on the fan base, every team does, and we're finally giving them a little bit of something to cheer for, and it's nice to hear them when we do come through," Cubs manager Rick Renteria said.
Hendricks isn't done yet. He is scheduled for one more start Sunday in the season finale against the Brewers at Miller Park. His 2.46 ERA is lowest among all Major League rookies with at least 10 starts this season.
"I definitely like having another after this one," Hendricks said.