After David Freese led off the fifth with a double, Dodgers starter Clayton Kershaw delivered a 1-0 fastball on the inner half of the plate, which clipped Ellis' glove and skidded behind him. That allowed Freese to jog to third base with no outs, putting him in position to score on Jon Jay's one-out sacrifice fly.
"It was a ball right down the middle," Ellis said of the passed ball, which appeared to be a strike despite home-plate umpire Mark Carlson's call. "I just missed it."
In a normal game, under normal circumstances, the play might not have mattered. But because Michael Wacha and a quartet of Cardinals relievers so thoroughly shut down Los Angeles' hitters, the run loomed large.
Jay understood the importance of that run, initially trying a squeeze bunt in an attempt "to get the job done any way I could." And Ellis knew it in the clubhouse after the game, shaking his head repeatedly when asked about the passed ball.
"I just missed it," he said multiple times.
As a result, one play came to overshadow all the good Ellis has done in this series. Though he is just 2-for-8 with a double through two games, Ellis crouched behind the plate for 13 innings in Game 1, guiding Zack Greinke to the best postseason start of his career. Then he caught eight more innings Saturday without an earned run.
Consider it an extension of the regular season, which saw Ellis rank fifth among NL catchers in defensive runs saved, an advanced metric designed to determine a fielder's overall value. He is an above-average defensive catcher by any measure, currently beating himself over one costly postseason mistake.
"It's just a lot of disappointment," Ellis said. "Frustration is a good word, too. We let two phenomenal starts get away from us. We can't waste starts like we got in Game 1 and 2 from Greinke and Kershaw and walk out of here not even with a split. It's pretty disheartening. We've got to regroup, use the off-day to get away from it and get back in front of our home fans and start mounting a big comeback to get back here to St. Louis."
Anthony DiComo is a reporter for MLB.com. Follow him on Twitter @AnthonyDicomo. This story was not subject to the approval of Major League Baseball or its clubs.