The Cardinals prospect broke a 4-4 tie with a two-run single in the bottom of the seventh inning and the Saugaros held on to defeat Peoria, 6-4, and move into first place in the Arizona Fall League's West Division.
Walsh also drove in another two runs on a base hit in the fifth, finishing 2-for-4 with a season-high four RBIs.
"I thought as a team we played well," he said. "We got down, 3-0, early but came back and scored runs when we needed to. We took the lead there in the seventh and didn't give it up."
Trailing by a run entering the bottom of the seventh, the Saguaros evened the score when Hanser Alberto (Rangers) grounded into a fielder's choice, scoring fellow Texas prospect Kellin Deglan from third. Walsh then came to bat and poked a grounder that tipped off the glove of Javelinas first baseman Vinnie Catricala (Mariners), scoring Alberto and Orlando Calixte (Royals) and giving Surprise a two-run cushion.
"I wanted to get something good to hit, probably try to get something into the outfield," Walsh said. "[We had] a runner on third with one out, so I was trying to hit something hard in the air. Then I got the two strikes and at that point I just wanted to put something in play. I hit it a little to the right of the first baseman and luckily it went though."
The 23-year-old is coming off a breakout regular season in which he shattered career highs in nearly every offensive category. Walsh led the Class A Midwest League with a .949 OPS, earning mid- and post-season All-Star nods, and ranked in the top three on Quad Cities in average (.310), home runs (16) and RBIs (68).
Walsh has been encouraged by his production in the AFL thus far, batting .250 with a homer and 10 RBIs in nine games. "I just wanted to continue with the approach I worked with this season, kind of continue the success I had," he said. "This season I started swinging the bat a little harder, so I want to keep that going throughout the fall and maintain good numbers.
"I think personally I'm playing well. I've had a couple of unlucky games, but who doesn't. I think I'm hitting the ball well pretty consistently."
Walsh benefited Wednesday from another stellar performance by Alberto. The designated hitter -- hitting ahead of Walsh in the No. 2 spot -- went 3-for-4 with two RBIs and two runs scored, his fourth consecutive multi-hit game.
The Javelinas took an early 3-0 in the top of the first but managed just one run the rest of the way. Mariners No. 5 prospect James Paxton (two hits over two scoreless innings) and fellow Mariners hurler Carson Smith held Surprise scoreless until the fifth.
Zack Cox is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.