If you think of a sports team as a train that’s powered by numerous, necessary engines, the Cardinals are showing the strain of so many injuries that have forced some of the engines to be replaced by lesser ones. While some of those replacements were great at the outset, as they continue to play, they continue to decline.

This isn’t an affront to players like Matt Adams, Shane Robinson and Adron Chambers, who have done a good job. But the reality of a situation like this is that there’s a reason starters start, reserves don’t, and minor leaguers are in the minors.

Adams was 13-for-34 in his first nine games, with six extra-base hits included. After that start, which had Adams at .382 with a 1.034 OPS, he’s gone 3-for-29 – hitting .103 with one extra-base hit – and his OPS has fallen to .737. Adams has six weeks of Triple-A ball under his belt. He shouldn’t even be here yet. And when pressed into duty replacing Lance Berkman and Allen Craig, it was going to be tough. And it has been tough for Adams in the last two weeks.

Robinson hit .419 in April, but has hit .206 since. Even though Robinson has had nine hits in his last 21 at-bats, he’s been at his best when Mike Matheny has been able to spot him behind Jon Jay or Skip Schumaker. When the job is his, Robinson has struggled so far. The same thing happened to Jay when Ryan Ludwick was traded two years ago. It takes time for some players to ascend, and that’s where an inexperienced Robinson is right now.

Chambers is 2-for-14 in his last six games after going 4-for-14 to start his major-league year. He’s gotten more time with both Jay and Schumaker on the shelf, and more playing time exposes a young player, sometimes too much.

Not only are the kids wheezing, but the weight of so many injuries may be affecting some established players. Matt Holliday had a sensational May, but is 6-for-20 with one double and a .624 OPS in June. David Freese has hit .217 since the start of May, although his slugging percentage has stayed near .500.

The point here is that this isn’t the Redbird team we envisioned. Nobody thought Yadier Molina would have to hit third, Craig would have to hit fourth, and that Robinson and Chambers would have to handle center field duties.

Fortunately for the offense, Rafael Furcal, Carlos Beltran and Craig have delivered more than anyone would have expected, and they’ve carried the offense so far. Beltran, in fact, might be the best position player free-agent acquisition the Cardinals have ever made. I figured him for 20 homers and 80 RBIs this season. He already has 18 and 46, a pace for 47 homers and 122 RBIs. If Beltran stays healthy, he could be the National League MVP.

The issues that have plagued the offense since the first weeks of the season are starting to take their toll on the pitching staff, too. The Cardinals were able to patch over the Chris Carpenter loss with a brilliant start to the season for Lance Lynn. But since Lynn left the bullpen and Kyle McClellan went down, the bullpen has scrambled, going through Brandon Dickson, Chuckie Fick and Maikel Cleto trying to replace him.

Now Jaime Garcia is hurt, and Joe Kelly turned in a representative performance in his major-league debut against Cleveland. One has to wonder if the pressure of pitching in a pennant race for a world championship club might be a bit much for a kid with two full pro seasons and a dozen games at Memphis.

As we saw last season, when all the engines are running, the Cardinals can be as powerful a train as there is in baseball. However, when powerhouses like Berkman, Holliday, Jay and Craig miss time, they put more pressure on the players who are in there, especially the kids up from Triple A.

And when stalwarts like Carpenter, Garcia and McClellan get hurt, moving Lynn to the rotation, that puts more pressure on not only the kids up from Memphis, but on Fernando Salas in the bullpen and strains guys like Jake Westbrook.

If they can get their DL guys back by early to mid-August, and stay within six or seven games of the lead, the Cardinals can have another great stretch run. But anything less than a full-strength Carpenter, Garcia, McClellan, Berkman, Jay, Schumaker and Holliday will slow this train down considerably, and probably make it late for the station at the end of September.