One swing. One dominant arm on the mound. And a whole lot riding on the outcome.

Monday night at Chase Field, the Arizona Diamondbacks and San Diego Padres kicked off a four-game series that could end up shaping who plays in October — and it didn't take long for the fireworks to start.

Let's talk stakes for a second, because this isn't just another midseason matchup.

Coming into Monday, the Diamondbacks sat at 59 and 53, holding a National League wild card spot after an absolutely blistering stretch of baseball since early July. The Padres weren't far behind at 58 and 54, riding a three-game winning streak of their own into hostile territory.

One game separated these two teams in the standings. That's the kind of margin where literally every single game swings the picture for October.

On the mound for Arizona was right-hander Brandon Pfaadt, and he picked a great night to look sharp.

Pfaadt worked through five scoreless innings against a Padres lineup that's been one of the hotter offenses in baseball lately. It was exactly the kind of outing Arizona has come to expect from him since he returned from a stint in the minors earlier this summer — he'd been nearly unhittable in his last several starts before this one.

On the other side, Padres starter Michael King came in with one of the better track records in baseball against Arizona specifically, but Monday night, the Diamondbacks had other plans for him.

And that brings us to the moment that really flipped the momentum.

In the fourth inning, Tim Tawa stepped up with runners on base and connected for a three-run home run off King. That swing alone gave Arizona a commanding lead and completely changed the energy of the ballpark.

It wasn't an isolated flash either — Tawa's been showing up in big spots against the Padres all season, and Monday night was just the latest example of him delivering when his team needed it most.

By the sixth inning, Arizona was firmly in control, with Pfaadt still dealing and the offense doing exactly what it needed to do against a Padres pitching staff that had been rolling coming into the night.

Zoom out for a second, and this game is really a snapshot of where both of these teams are right now.

Arizona has been the hottest team in the National League since the start of July, and their manager has talked about how this stretch of the season is where contenders really separate themselves from everybody else. San Diego, meanwhile, has answered every step of the way, refusing to let the Diamondbacks pull away in the standings.

With this being the opener of a four-game set, both teams know there's a lot more baseball left to play in this series — and every single game is going to matter for the wild card race down the stretch.

So that's where things stood as this series opener unfolded — Pfaadt dealing, Tawa delivering the big blow, and two playoff hopefuls just getting started in a series that's going to matter a lot more than one box score.

We'll keep bringing you the latest as this series plays out, so make sure you're subscribed so you don't miss it.

Drop a comment and let us know — do you think the Diamondbacks can hold onto that wild card spot? See you in the next one.