He entered Saturday fourth in the National League in ground-ball-to-fly-ball ratio (2.71), but 43rd in strikeouts per nine innings (4.48). And for the first three innings, he held Cubs batters at bay, tossing eight pitches in each inning and coaxing nine ground-ball outs.
Mulder guarded a 1-0 lead entering the top of the fourth inning. And that's when everything fell apart.
The Cardinals couldn't handle three fourth-inning chances by their top three defensive players -- David Eckstein, Scott Rolen and So Taguchi.
Mulder couldn't pitch around the miscues and the floodgates opened for a five-run inning that led to an 8-5 Cardinals loss.
The inning started with another ground ball: a slow hopper from Neifi Perez that Eckstein had to charge at short.
Entering the game, the slick fielding shortstop was in the top five among National League shortstops in fielding percentage (.984) and fewest errors (4).
This time, though, Eckstein committed his first miscue since May 22. He charged and gloved the ball cleanly, but threw wild past first base, one-hopping the fence guarding the Cardinals' dugout.
"He made the pitches and some of those plays, it was just one of those things," Eckstein said. "On my ball, I was just trying to make a play. And it was slow hit and I was just trying to come in."
After a single by Michael Barrett, Mulder delivered another ground ball from Phil Nevin to his other reliable source on the infield: third baseman Scott Rolen, arguably the best in the game at the hot corner.
On Friday night, with bases loaded and one out, Rolen let a potentially game-ending double-play ball slip through the five-hole and go into left field, tying the game at 4.
This time, he had difficulty with Nevin's grounder. He moved to his left and charged the ball on the infield grass, but couldn't pick the short hop cleanly, leaving Mulder in a bases-loaded, none-out jam.
"I think it was a lot different after that," St. Louis catcher Yadier Molina said. "Those things happen. A Gold Glover like Rolen and Eckstein, it's hard. A lot of things happen."
Mulder tried to shake it off, saying afterward that mistakes are part of the game.
"It's happened before, those are errors that are going to happen," Mulder said. "Those happen sometimes and neither of them were really easy plays. Eckstein was coming in on it and Rolen was trying to cut that ball off, and it's not like those are routine plays. Those are errors and errors happen."
But Mulder couldn't pitch around the base runners. Three pitches later, Aramis Ramirez unloaded on a 2-0 Mulder fastball, parking the pitch in the right-center field bleachers for a grand slam and a 4-1 Cubs lead.
Mulder opened the wound even further when Matt Murton and Jacque Jones followed with first-pitch singles.
Jones' hit led to the third mistake. So Taguchi charged the ball in center, but the fundamentally sound veteran didn't get his glove down all the way and Murton advanced to third.
Ronny Cedeno hit a run-scoring single to right, easily scoring Murton -- and giving the Cubs a comfortable 5-1 lead. The Redbirds wouldn't get any closer until the ninth.
"With Mulder, you know that you are going to get a lot of ground balls and that's one of the reasons why he is so good," second baseman Aaron Miles said. "There were some tough plays and then he leaves one ball up and it gets out of hand."
And the fourth inning -- and the game -- certainly did for Mulder and the Cardinals.