SURPRISE, Ariz. -- What began as a pitchers' duel on Saturday turned into a back-and-forth contest before the West walked it off on a single by Royals catching prospect Meibrys Viloria to edge the East, 7-6, in the 13th annual Arizona Fall League Fall Stars Game at Surprise Stadium.:: 2018

SURPRISE, Ariz. -- What began as a pitchers' duel on Saturday turned into a back-and-forth contest before the West walked it off on a single by Royals catching prospect Meibrys Viloria to edge the East, 7-6, in the 13th annual Arizona Fall League Fall Stars Game at Surprise Stadium.

:: 2018 Arizona Fall League Fall Stars Game ::

The West rallied to score two runs with two outs in the bottom of the ninth inning after Vladimir Guerrero Jr., MLB Pipeline's No. 1 overall prospect, had reached second on an infield error to open the frame. Buddy Reed tied the game with a two-out triple off the wall in left-center field that plated Guerrero and set the stage for Viloria, who roped a line drive into the right-center-field gap for the walk-off win.

"It was down and a little out," said Reed, the Padres' No. 13 prospect, about the clutch hit that helped earn him MVP honors. "I put a good swing on it, Justin [Lawrence] pitched his butt off. I had to choke up because he's a little uncomfortable for me, just throwing 98 to 100 with sink … so just choked up and tried to put a good swing on it."

Starting pitchers Forrest Whitley and Nate Pearson treated fans to some early excitement, as each hurler showed triple-digit velocity out of the chute.

Pearson, the Blue Jays' No. 4 prospect (No. 90 overall), was electric in his lone inning as he topped out at 104 mph with a fastball that never dipped below 101 mph. At one point he threw three consecutive 103 mph fastballs, and he paired his heater with a nasty cutter/slider at 95-96 mph that he used to induce a swinging strikeout of Monte Harrison . He struck out two in the frame.

"The highest I've ever hit before today was 102 mph," Pearson said. "I saw 104 mph and I was kind of skeptical of it was actually real, but everyone in the dugout was freaking out, so I guess it was pretty legit.

"I knew I was only going one inning so I was just going to let it go … really try to throw as hard as I can and give the guys my best stuff."

Peter Alonso, the Mets' No. 2 prospect, was the lone hitter to best Pearson, as he put the East on the board in the first with a two-out, 400-plus-foot solo home run to center field. Alonso's blast came on 103 mph fastball from Pearson and had an exit velocity of 110 mph.

"[Pearson] was throwing some noise up there," Alonso said. "With a guy like that you pretty much need to swing as soft as you can and let the pitcher supply the power. Thankfully I got a fastball to hit up in the zone, and I capitalized on it."

Whitley, MLB Pipeline's top-ranked pitching prospect, was up to 100 mph with his heater, which sat comfortably in the mid- to high-90s during his two scoreless frames. The 21-year-old right-hander showed good feel for his low-80s changeup as well as a cutter and slider, while also mixing in a curveball.

"That's actually the first time I've hit 100 since high school," said Whitley, the Astros' No. 2 prospect, after tossing two hitless frames with two walks and one strikeout. "The location and command was a little bit sporadic, but that's fine. In a game like this you just try to go out there and show your best stuff, and I feel like I did OK with that."

With both starters out of the game, Brewers top prospect Keston Hiura plated the Yankees' Estevan Florial, who hit a leadoff triple off D-backs top pitching prospect Jon Duplantier, with a sacrifice fly to even the score.

The West grabbed their first lead of the game in the following frame when Toronto's Cavan Biggio scored on a passed ball, and Dodgers No. 2 prospect Keibert Ruiz tacked on another run with an RBI single to center field.

After an RBI single by D-backs first-base prospect Pavin Smith in the top of the fifth had cut into the West's lead, Guerrero led off the bottom half by hammering a hanging breaking ball off the wall in left field for a double and advanced to third on an errant throw.

The 19-year-old third baseman's rope, his lone hit in four at-bats, had an exit velocity of 117 mph. For context, only 15 Major League players have registered hits on balls hit 117-plus mph since Statcast™ debuted in 2015.

Austin Listi, an outfielder in the Phillies' system, knotted the score in the sixth inning on a groundout to shortstop, only to see the West reclaim the lead in the bottom of the frame on pinch-hitter Yu Chang's two-run triple to the right-field wall. The hit by the Indians' No. 6 prospect had an exit velocity of 110 mph.

The East, however, responded in a big way in the eighth, as Listi connected on a three-run homer to left field with two outs to put his team back on top. Listi's homer, his first of the Fall League, came on a 2-2 offering and had an exit velocity of 101 mph. He finished the game 1-for-2 with four RBIs.

Viloria's walk-off hit capped a 2-for-3 performance. He was the lone West hitter to record multiple hits and did so despite entering in the sixth inning as a replacement.

Mike Rosenbaum is a reporter for MLB.com. Follow him on Twitter at @GoldenSombrero.