SURPRISE, Ariz. -- It’s not often that Arizona Fall League games end with sports drink baths on the infield dirt and teammates streaming out of the bullpen to celebrate. At the heart of Surprise’s seesaw 8-7 walk-off victory over Salt River on Thursday was Donovan Casey.

Still clad in an orange-soaked uniform, the Nationals' No. 18 prospect was effusive in his praise for the Saguaros, who rallied for four runs in the bottom of the ninth to win their fifth game in a row.

“The competition is always there,” Casey said. “Our whole team, we go out there and compete. We never gave up in the last inning.”

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Opening the floodgates for that never-say-die attitude was Casey, who ripped a double to the gap in left-center field with one out in the ninth. He crossed the plate on a game-tying three-run single by Yankees No. 6 prospect Austin Wells, before Seuly Matias (Royals) stung a walk-off single down the left-field line.

Prior to the late-game theatrics, Casey staked Surprise to a four-run lead with his first homer of the Fall League campaign, a three-run blast to left. Known primarily for his speed and defensive acumen, the 25-year-old delivered multiple extra-base hits in the game, something he accomplished just five times during the regular season.

“I just go in there and try to make hard contact; I look for barrels,” Casey said. “I’ve been working with a lot of the hitting coaches and [had] guys trying to help me out, get my swing right, feeling good in the box.”

When Max Scherzer and Trea Turner were dealt to the Dodgers in a blockbuster deal at the July 30 Trade Deadline, a quartet of prospects came back to the Nationals, two of whom -- Keibert Ruiz and Josiah Gray -- have already graduated. But Casey, a former L.A. farmhand selected in the 20th round of the 2017 Draft, remains in the Washington pipeline.

After batting .347 with a .965 OPS in 12 games at Double-A after the trade, the Nationals quickly promoted Casey to Triple-A Rochester, where he scuffled across 38 games.

“I just tried to stay the same,” Casey said of his arrival in a new organization. “Obviously, I went through a point where I struggled a little bit, but it’s baseball. I just try to stick to the same routine every single day and just try to keep getting better and keep building off what I’ve been doing all season.”

Now among the cream of the collective prospect crop in Arizona, Casey is cognizant of the level of competition he faces on a daily basis. Calling the competitive nature of the Fall League “about the same” as that of Triple-A, his first taste of success on the circuit bodes well as he looks to knock on the big league door entering 2022.

The starting rubber for Surprise on Thursday provided a reminder of how stellar some of the featured arms can be.

Third-ranked Royals prospect Asa Lacy boasts three 60-grade pitches in his arsenal, per MLB Pipeline -- his fastball, slider and changeup. Against Salt River, he deftly utilized all three -- in addition to his curveball, compiling five strikeouts over three scoreless frames.

Lacy’s latest dominant outing gives him 15 strikeouts across 7 2/3 innings during the Fall League. The exorbitant punchout totals far exceed the 13.7 K/9 he racked up during a 14-start stint during his professional debut at High-A Quad Cities this season.