The Cardinals have exceeded expectations with a 17-8 start that includes a +36 run differential, tied for the second-best mark in MLB with the Blue Jays. The underlying performance in those numbers is good as well: the Cards are second in the NL in OBP, third in SLG, and second in runs scored. They’re tied for fifth in runs allowed, with a 2:1 K/BB ratio and the second-fewest home runs allowed in the league.

If that last part sounds familiar, it should. The Cards’ strong start a year ago was driven by an extremely soft schedule and a flukishly low home-run rate. Once pitchers such as Kyle Lohse, Braden Looper, and Ryan Franklin began giving up home runs as expected, the Cards’ pitching didn’t look quite so good. They did finish 86-76 thanks in part to the strong start, but they weren’t a factor in the races for either the NL’s Central title or Wild Card.

Well, we’re back there again. Lohse has allowed just one homer in 32 innings. Joel Pineiro, playing the part of the departed Looper, has given up two in 33 1/3 innings. Franklin has yet to allow a home run, or a run, in 10 1/3 innings. Todd Wellemeyer, not pitching well, would have an ERA even higher than 5.28 if he’d allowed more than a single bomb in his 29 innings.

Some of this is a marked tendency toward getting ground balls. Pineiro has a 69/26 GB/FB ratio this season, and both Lohse and Wellemeyer are close to two ground balls for every fly ball. Even Franklin, a notorious fly-ball pitcher, is at 12/6. This is Dave Duncan‘s influence, as all of these pitchers were more prone to putting the ball in the air before they got to St. Louis. Turning these pitchers into a ground-ball staff has been a remarkable achievement, and a big part of the Cards’ success the last two years.

With that said, the home-run rates by the starters are not sustainable.

                2009           2008
            HR   FB   %    HR   FB    %
Lohse        1   26   4    18  152   12
Piniero      2   26   8    22  137   16
Wainwright   1   27   4    12  103   12
Wellemeyer   1   23   4    25  174   14

The Cardinals may give up a below-average number of homers because their starters won’t put the ball in the air as much as their peers do, but they will give up more-twice as more on a per-fly ball basis-as they have so far this season. This isn’t a particularly good defensive team-12th in the league in Defensive Efficiency, 11th in PADE-so the rotation’s tendency to put the ball in play, coupled with an uptick in homers allowed, will bring the run prevention more in line with what was expected at the start of the season, and chip away at that .680 winning percentage.

The bullpen doesn’t have the same issue with HR/FB collectively, but it is anchored by a Ryan Franklin with a zero ERA, so skepticism is warranted. However, the live arms of Kyle McClellan, Jason Motte, and Chris Perez make this the most skilled pen that Tony La Russa has had in some time. The role assignments have been a little quirky, and will likely be fluid throughout the year, but it’s not hard to see this pen being an asset in 2009.

Can the Cardinals hit their way into the postseason? With a .283 EqA so far, their offense has been second only to the Dodgers in MLB, but that’s been put up by a mix of guys playing way over their heads and guys having awful seasons. Albert Pujols is at .356/.468/.724, which is stunning even by his lofty standards. I can’t wait to see who gets the MVP instead of him this year.

(Side note: Am I the only one who feels as if triple-slash stats can never again be truly jaw-dropping after the Barry Bonds Era? Say what you will about the man and the issues surrounding him, but he had a .609 OBP one year, and an .863 SLG in another. He was intentionally walked 120 times in 2004, when he drew 232 walks in total. Over the last seven years of his career, Bonds has more intentional walks than strikeouts. Albert Pujols is great, really great, but when it comes to his effect on the opposition, he’s not in Bonds’ league.)

In addition to Pujols, Yadier Molina is continuing his development into a two-way threat, paralleling the career path of Ivan Rodriguez (albeit on a less-elevated track). He’s at .329/.393/.481, with nine walks and nine strikeouts. Chris Duncan is apparently healthy again, batting .312/.413/.558, with only the batting average being particularly inflated. Duncan’s play has eaten into Colby Rasmus‘ playing time, but the rookie has batted .270/.365/.365 so far, which is a positive.

Despite David Freese spitting the bit, even third base has been an asset thanks to the best month of Joe Thurston‘s life, and Brian Barden‘s with it. Overall, Cardinals third basemen are batting .281/.356/.416, which is very probably the dream scenario for a team still hoping to get Troy Glaus back this summer.

At the other end of the spectrum you have the middle infield of Skip Schumaker (.266/.337/.329) and Khalil Greene (.215/.329/.338), both failing to produce at the plate while also being part of the Cards’ overall defensive issues. Brendan Ryan (.250/.317/.389) has been the best of the group, platooning with Schumaker and making a bid for a larger role. Rick Ankiel hasn’t built on last year, hitting .256/.326/.405, though if you combine what he and Duncan have done, you’re about par for the course for the two players.

Overall, this offense is unlikely to continue being among the best in the league. Molina, Thurston, Barden, and Duncan… even Pujols… are all candidates to slip a bit, and there’s not enough projection in the rest of the lineup to make up for that. Schumaker’s 2007-08 peak was nice, but he has to hit .300 to help a team whether he’s a good left fielder or a bad second baseman. Greene has improved his command of the strike zone at the cost of his power, which is a tradeoff that might work if he can hit .270. He may also be someone whose short peak is gone. Ankiel and Duncan, combined, are likely to match the current level of production; same for Ryan Ludwick, who’s picked up basically where he left off last year.

Are there other ways to get better? Playing Rasmus over Duncan more often would help the defense, but Duncan has a 971 OPS, which makes him hard to sit. If you play Ryan over Schumaker, you upgrade the defense a little, but Ryan is a worse hitter than he appears to be, and you’d have the collateral effect of having no place to play Schumaker, who can’t crack this outfield. The ideal scenario is the same as it was over the winter, when trade rumors involving Ludwick for a second baseman never became a reality. Give the team all of the credit in the world for the Schumaker play, which was an outside-the-box gambit, but the Cardinals’ issue is exactly what it was six months ago: four outfielders, one DH, and no second baseman.

The solution is to trade the pitching coach’s son for a second baseman, which is probably as politically dead an idea as it was when I suggested it a year ago. Still, would a Duncan-for-Luis Valbuena deal be a fit for Cleveland? To the Angels for Brandon Wood? It’s a little hard to find an AL team that has second-base depth to move.

One thing that can’t be held against the Cards this year is their schedule. They’ve played six games against the Cubs and three against the Mets, Diamondbacks, and Braves. Last year’s hot start was against the weakest slate in the game deep into May; this year’s is against a more representative slate of opponents. No demerits there. They’ll have a chance to set the season’s narrative this month, as after hosting the Phillies for two games this week, they play 14 straight games against NL Central foes, including six with the Brewers and three at home against the Cubs. By Memorial Day weekend, we’ll have a much better read on this team.