CHICAGO -- After a conference on the mound, the Reds called Nick Castellanos in from right field and positioned him at third base. With Jason Heyward in the box, runners on the corners and the game on the line, Cincinnati employed a five-man infield.

Heyward rendered the defense moot with a blast off the video board in right field. The outfielder pulled a slider from reliever Brad Brach into the North Side night Wednesday, delivering a 4-1 walk-off win in the 10th inning.

"That's a fun way to end a baseball game," Cubs bench coach and acting manager Andy Green said. "A guy as good as J-Hey hitting a baseball like that."

It has been a trying offensive season for Heyward personally, and a campaign full of ups and downs for Chicago as a whole. That has made this latest stretch -- eight wins in the past nine games -- enjoyable for a group trying to end the year on a high note.

"This is the first time in my career being in that position to play spoiler," Heyward said of beating a Reds team in the National League Wild Card hunt. "It's a lot of fun playing good baseball, of course. But when you have some incentive to do it and go out there together, it's really nice to see results."

Here were three key performances within the Cubs' victory:

1. Mills keeps rolling in rotation

Alec Mills does not have a clear explanation, but the Cubs’ right-hander is thrilled that his move back to starting has coincided with consistency. Surely, his performance over the past few months will position him well for the 2022 rotation.

"I'm just going to keep rolling with it," Mills said. "I'm throwing well, so let's keep doing it."

Against the Reds, Mills logged six strong innings, in which his lone setback was a solo homer off the bat of the always-dangerous Joey Votto. Mills struck out three, walked one and scattered four hits in a no-decision.

With that showing, Mills now has a 3.53 ERA with 59 strikeouts against 16 walks in 81 2/3 innings in the rotation this season. He has thrived with the five-day routine, as opposed to the unpredictable life of a reliever (6.41 ERA in 12 games).

In fact, this falls in line with Mills' career production. The righty has a 3.81 ERA with 144 strikeouts against 44 walks in 174 2/3 innings (33 starts) as a member of the starting rotation. As a reliever, he has a 5.24 ERA in 25 career appearances.

"He's a guy that has pitched through some really good lineups," Green said, "and done a little bit of everything with the baseball; sinking it, cutting it, spinning it, throwing the changeup, throwing that 60-mph breaking ball that not many other people have. He's really stabilized our rotation."

2. Happ's power surge persists

In the hours leading up to Wednesday's game, Green was asked for his take on outfielder Ian Happ's recent offensive tear. Specifically, the bench coach was asked about Happ's recent propensity for getting the ball in the air.

"My opinion, watching him," Green said, "is he's been more aggressive early in the count. He's been willing to play things out in front a little bit more. When the contact point's moved a little bit further out in front, usually it gets hit in the air a little bit more consistently."

It did not take Happ long to show what Green meant.

In the first inning, Happ turned on an 0-1 fastball from Reds righty Vladimir Gutierrez and sent it a projected 444 feet to the top of the right-field bleachers. That marked the third game in a row with a homer for Happ, who now has 21 shots on the year.

Back on Aug. 12, Happ's season OPS dropped to .599 and he sported a 68 wRC+ (32 percent below MLB average). In the 24 games since that point, he has hit .371/.404/.787 with 10 homers and 22 RBIs. He is up to a .730 OPS and 98 wRC+ on the year.

"That's Ian Happ," Heyward said. "Seeing him finish out the season and be who he is and take advantage of more playing time is really fun to watch."

3. A look at late-inning future

With Votto looming in the seventh inning, Green knew he had asked enough of Mills. The Cubs' bench coach planned on leaning on Rowan Wick and Codi Heuer for the final three innings.

As it happened, Wick and Heuer wound up working two innings apiece, with the latter keeping the automatic runner at second base in a clean 10th inning.

"Any time you're going to come in in that 10th inning," Green said, "and not let that runner move at all, that's special. That's fun to watch. He's very poised out there, very relaxed in tense situations."

Heuer -- acquired from the White Sox prior to the Trade Deadline -- has spun an 0.86 ERA in his last 21 innings, with no earned runs allowed in his past dozen appearances. Wick, who spent most of this season on the injured list, has a 2.63 ERA in 12 games since being activated.

The Cubs' bullpen as a whole has turned in an 0.84 ERA (four earned runs in 43 innings) over the past nine games. That development has been cause for some optimism as the team evaluates internal options with 2022 in mind.

"All those things are really encouraging signs as we move forward here," Green said. "Both those guys [Wick and Heuer] did huge things for us today."