Thursday’s 5-3 Cardinals loss in 11 innings to San Diego, in and of itself, isn’t a big deal. It’s the opener. Dropping the opener with 161 games left is no big deal in the big picture.

However, in the small picture, this loss is what worried me about the Cardinals during spring training. This is a club with little margin for error overall. They can’t afford to lose a player because of their lack of depth. They don’t have margin for error in individual games, either. There are numerous examples from Thursday’s game.

Bottom of the third, Cardinals up 1-0. Ryan Theriot and Colby Rasmus reach first and second with nobody out, but the great Albert Pujols grounds into a double play.

Bottom of the fourth. After San Diego tied the game at one, the Redbirds retake the lead on Yadier Molina’s RBI hit to center, which puts runners at first and second with no outs again. However, the rally ends when Skip Schumaker grounds into the second Cardinals double play of the day.

Top of the fifth, after a Ryan Ludwick walk. Chris Carpenter retires the next two. But Ludwick steals second on Cameron Maybin’s swinging third strike, with Schumaker dropping a nice throw from Molina. The next hitter, Nick Hundley, doubles on a 2-0 pitch to tie the game at two.

With a 2-2 score in the bottom of the sixth, Matt Holliday gets picked off second base with Lance Berkman at first and nobody out. Then David Freese flied out and Molina grounded out to end the inning.

Bottom of the seventh. After Daniel Descalso bunts Schumaker to second, Ryan Theriot grounds out and Colby Rasmus strikes out to end the threat.

Bottom of the ninth. Ryan Franklin allows a first-pitch homer to Maybin, who struck out 92 times in 291 at-bats last year.

Top of the 11th. After Bryan Augenstein retired the first two batters, Chase Headley singles, and then Maybin also singles. But Theriot mishandles the throw into second, and Headley scores the winning run.

To summarize, that’s four runners at second with no outs or one out that weren’t plated by the Redbirds. Pujols, Schumaker and Theriot each failed in those situations, and Holliday was picked off. In addition to those miscues, Pujols uncharacteristically grounded into three double plays after grounding into just 23 last year in 700 plate appearances.

In the field, Schumaker dropped what would have been the third out on Maybin’s strikeout in the fifth. Franklin hung a pitch to a strikeout machine with two outs in the ninth, and Theriot’s error allowed the winning run to score.

The mistakes on defense and the inability to get runners home from scoring position with less than two outs caused the Cardinals to waste a masterful opening-day performance from Carpenter, who went seven innings, and allowed two runs on just two hits, with four strikeouts and two walks.

The way the Cardinals are set up, they are going to play a lot of close games. They’re going to rely on Pujols and Holliday homers to win those close games, and when they get those homers, the bullpen is going to have to nail down victories. There were a lot of positives in the Redbirds opener, including Rasmus going 2-3 with a couple of walks, Holliday going 3-4 with a couple of RBI and the go-ahead homer, and David Freese turning in two stellar defensive plays.

But while the Cardinals lost, the defending division champion Reds rallied, and got a three-run homer to beat Milwaukee in their opener. Unlikely hero Ramon Hernandez hit the blast, and it came after the Reds had rallied from a 3-0 deficit and a 6-3 Brewers edge to start the ninth. So while the Redbirds did more of what they did in 2010, the Reds did too; coming through in the clutch and winning a game late.

While there were highlights, the Cardinals simply can’t squander opportunities that present themselves during games, and they can’t give away outs. There are teams, like the Cardinals clubs of 2004 and 2005, who can overcome mistakes by bludgeoning opponents. This edition of the Redbirds isn’t one of those. They’ll have to get to the late innings and win games by not making mistakes. If they do, then Thursday’s game will simply be a microcosm of this season’s 162 games.