Worse still, it was the third time on the trip that the Cardinals squandered what may be their greatest asset: their top two starting pitchers. St. Louis went 0-3 in games started by Chris Carpenter and Adam Wainwright during the western swing, missing out on critical opportunities at a time when two-fifths of their starting rotation is on the disabled list.
"It's a special opportunity when you've got one of the big guys," said manager Tony La Russa.
The D-backs' Chris Young hit a two-out, two-run walk-off homer in the ninth inning that was the telling blow. Miguel Montero kept Arizona alive with a two-out single against Kyle McClellan in the ninth, and Young drilled an 0-1 fastball into the left-field seats to end the game. St. Louis had rallied for three runs in the top of the ninth against Chad Qualls and Esmerling Vasquez, tying the score on a wild pitch by Vasquez after RBI singles by Albert Pujols and Randy Winn.
McClellan continued a disconcerting pattern in which he has been hit hard throughout his career in tie games.
"[The pitch to Young] started outside and it came back middle," McClellan said. "I think the whole inning comes down to the at-bat before. The 2-2 curveball, I missed with that. If I make a pitch there, it's over, and we're not in that situation.
"I threw a breaking ball [to Montero] and missed high. If I can get it over the plate, maybe he takes it or chases it. And then at 3-2, you can't walk him there. So you've got to almost throw it down the middle and hope he hits it at somebody, because you don't want to walk. You want to make him earn his way on for the winning run."
It was the second homer of the game for Young.
"I knew it had a chance," Young said. "I was yelling at it, hoping it would get up, and luckily it did."
The runs capped a substandard afternoon for the Cards' bullpen, which has held leads very well -- but nonetheless allowed five walk-off home runs this year. Dennys Reyes also struggled, allowing two runs in the seventh after the Cards got on the board for the first time half an inning before.
The Cardinals finished their six-game road swing with a 1-5 mark, winning only Friday night's game against the D-backs. They remain 1 1/2 games behind the first-place Reds in the National League Central after Cincinnati lost at home to the Royals.
Carpenter wasn't overwhelming on Sunday, but he was good enough that on plenty of occasions, he would have won. He survived six innings with three runs allowed, needing 117 pitches to do so. Carpenter worked out of a bases-loaded, no-out jam in the fifth, and a two-on, one-out situation in the sixth before he was lifted.
"They put good at-bats on me the whole game, fouling some tough pitches off," Carpenter said. "But I was able to continue to make pitches when I had to make pitches and give my team a chance. At least keep them in the game a little bit."
Carpenter departed the game facing a 3-0 hole before his offense came alive in the seventh. That's when Pujols broke through with a two-run double against reliever Aaron Heilman. Yet immediately after the visitors got back in the game, Reyes gave the runs back. Reyes permitted hits to three of the four batters he faced as Arizona stretched its lead back to three runs. Reyes has been charged with runs in three of his four June appearances, recording two outs -- total -- in those games.
Yet the Cardinals still fought back, getting three runs against the beleaguered Arizona bullpen before letting the game get away in the bottom of the ninth. They send Wainwright to the mound on Monday at home, once again hoping to capitalize on a big chance.
"It's not like we don't have confidence in our other pitchers, but yeah, those are two guys that we expect to win every single time," said Skip Schumaker. "Having said that, we need to put runs on the board. We didn't exactly help provide them with any cushion. They kept us in the game every single time and we didn't do anything for them. That's a problem. I do believe those are must-win games. But it's on us that we didn't help out."
Matthew Leach is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.