Spangenberg doubled to start the inning, moved to third base on a bunt by Clint Barmes and scored when Wallace hit a ball to shortstop Jose Reyes, who threw home late.
San Diego rookie Colin Rea, who was making his sixth career start, tossed seven scoreless innings, allowing just two hits and striking out four. He was in line to win before closer Craig Kimbrel allowed a two-out home run to Nolan Arenado in the ninth inning to tie the score.
Colorado rookie pitcher Jon Gray didn't factor in the decision but pitched well, allowing two hits over five scoreless innings with six strikeouts.