Arroyo Seco iced the game in the fifth after scoring four runs and taking an 8-0 advantage.
With out one, Saints designated hitter Corey Sims reached on an error, which was followed by back-to-back singles from Crescenta Valley High graduate Troy Prasertsit (three hits and two runs) and Jonah Jarrad, whose hit scored Sims.
After another error allowed third baseman Dom Davis to reach to load the bases, the contest then fell apart for Lacey on the very next pitch.
Starting hurler Bryan Lounsbery tossed a wild pitch that scored two runs when catcher Jordan Churchill recovered the ball at the backstop and then frantically threw past the plate toward the infield.
Prasertsit scored on the wild pitch, while Jarrad came home on the throwing error and Davis took two bases.
On the pitch after the wild pitch, pinch-hitter Josh Clark delivered a sacrifice fly that completed the inning's scoring.
"I thought the difference was the routine plays. We made them and they didn't," Prasertsit said. "When you make the routine routine, you're going to win ball games."
Arroyo Seco added a run in the sixth on a RBI double from St. Francis alumnus Tei Vanderford (three hits and two RBI).
The Saints started the game with a run in the first on a RBI single from Vanderford followed by two runs in the second on three doubles from Prasertsit, Davis and Cal State Fullerton-bound David Olmedo-Barrera (St. Francis).
Arroyo Seco's pitching may have been most impressive, as the Rio Hondo League combo of Temple City High's Calvin Copping and San Marino's Jeff Bain combined for a three-hitter with eight strikeouts versus two walks.
"I just went up there, threw strikes and got outs. That's what it's about," Copping said. "I knew Jeff was a pretty good pitcher and it was nice to have him back me up."
Copping tossed four innings of work and allowed only two hits, while escaping a two-on, no-out jam in the second inning by inducing a double play followed by a ground out.
ARCADIA ASTROS 4, LOS ALTOS BRONCO 3 (eight innings)
Crescenta Valley product Ted Boeke finished two for four for the Astros, who received a go-ahead homer in the top of the eighth from Pasadena Poly's Zachary Bern in winning their Palomino Tournament opener and advancing to Saturday's second round at 7:30 p.m.
Arcadia led, 3-1, heading into the bottom of the seventh, but surrendered two runs, while Los Altos loaded the bases.
However, just-inserted reliever Davey Feess (Pasadena Poly) recorded a strikeout to escape the jam and then punched out Los Altos' Eugene Kim in the eighth with a runner on second that secured the win.