Heyward's two errors in right field in the series, his only two of the season, signify his first stretch of consecutive games with errors since 2011.
"I should have pulled up sooner," he said of the David Peralta line drive he misplayed, which ricocheted off Heyward's body and rolled toward the right-field corner, allowing Cliff Pennington to score the tying run and Nick Ahmed to score from first to give Arizona a 3-2 lead in the sixth.
The first-year Cardinal atoned for the miscue in his final at-bat, launching a no-doubt blast off Brad Ziegler that slipped inside the right-field foul pole in the ninth.
"To be up in a big spot and tie the game, it's awesome, and you can do that regardless of whether you messed up before or not," said Heyward, a two-time Gold Glove Award winner.
His Tuesday-night error came on a similar play to Wednesday's. Heyward said he is still adapting to a new outfield after spending the first five years of his career with Atlanta.
"I'm going to get more comfortable with it, and on that play, I was really over-aggressive," Heyward said. "[Manager] Mike [Matheny] said he would like to see me be more aggressive. Some balls it's going to look like I can get to that I have no business getting to, and I should just play it off the hop and get it in."
David Cobb is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.