By Marc Normandin

The Washington Nationals had excellent pitching in 2012. The same five arms made 150 of the team's 162 starts, with a 3.40 ERA in a league in which the average starter put up 4.04. If Stephen Strasburg hadn't been on his famed innings limit, they very well could have had fewer than 10 of their games started by non-regular rotation members. That was 2012, though. The 2013 season is a totally new one, and just because Strasburg is going to be let loose this time around doesn't mean the Nationals are going to do better with their rotation. In fact, history -- and the context of the Nationals' rotation itself -- are both likely to get in the way of that.

Let's jump back to 1998 temporarily. That's when 28 Major League Baseball teams became 30 with the addition of the then-Devil Rays and the Diamondbacks. Since that year, there have been 450 different team seasons -- 30 teams, each playing a full season, multiplied by 15 seasons. Of those 450 team seasons, just 24 of them have resulted in the kind of health and consistency that the 2012 Nationals displayed. That is, just 24 of them have managed to roll out five starters with at least 27 games started apiece. For those who love their percentages, that's just over five percent of all teams in the last decade-and-a-half. Want to dial it back to 26 starts for the minimum? You get 31 teams, or less than seven percent. For 25 starts, 36 teams and eight percent. Five starters making at least 25 starts might not sound impressive, but it's a rare occurrence, and not one that teams can necessarily rely on repeating. You get the idea.

To bring it back to what the Nationals actually did -- 27 starts at minimum -- just one team in the last 15 years has managed to repeat the feat. The 2004 and 2005 St. Louis Cardinals each pulled it off, with the 2004 iteration getting at least 28 starts from each of their five, while the 2005 version is one of just six teams since 1998 to get at least 30 starts out of each rotation member. A few clubs were able get that performance twice over three-year spans, but the Cardinals stand alone as far as back-to-back goes. The Nationals have a chance of doing this, given their impressive rotation, but as with every other rotation in baseball, the odds are stacked against them.

Stephen Strasburg might be the best pitcher in baseball. He might not be that guy at this very moment, but his career is basically a countdown to the moment it happens, whether that's during the 2013 season or it takes until 2015, or whenever it is that Justin Verlander decides to stop hogging all the glory. What we don't know about Strasburg just yet is how many innings he can throw in a season. In 2012, he tossed 159 frames, and while he was limited by his recovery from Tommy John surgery, in actuality, he set a career-high workload. His 2010 was cut short after 123 innings, and thanks to that same surgery, he tossed all of 44 innings in 2011 between rehab starts and his reemergence in the bigs.

Strasburg might not be at an increased risk of further injury than any other pitcher out there, but all we've seen him do is throw 159 innings on a 28-start schedule where he was babied a bit (with good reason) by the Nationals. He could very well jump that inning total up another 30, and give the Nationals 28 starts or more again, but that's the kind of thing that has to be penciled in, as he has no history of doing it just yet. It's likely, but not a given.

Jordan Zimmermann made 32 starts and threw 195 innings for the Nationals in 2012, and posted a shiny 2.94 ERA in the process. There are reasons to be, if not concerned, at least a little wary, about him going forward, though. For one, Zimmermann struggled in the second half, thanks in part to a batting average on balls in play that shot up to .321 from the first half's .272. Now, that could be poor luck and small sample size, but there are some flags worth mentioning here.

Zimmermann has great control, but the fact he struggles to consistently put hitters away, even when ahead, suggests command isn't his strength. Zimmermann also sees an exceptionally high percentage of his pitches fouled off, and is predominantly a fastball pitcher -- knowing a certain pitch is likely on its way, one without a ton of movement that is liable to be somewhere your bat can get to it, means a whole lot of foul balls. This kind of thing wouldn't show in his strikeout-to-walk ratio -- which are admittedly impressive -- but it can manifest itself in other numbers, such as homer rate, BABIP and Zimmermann's surprisingly low innings total for someone with 32 starts in a season.

Baseball Prospectus' Ben Lindbergh -- who also pointed out Zimmermann's tendency to see his fastball fouled off -- seems to think Zimmermann might throw too many fastballs as part of the pitcher's mission to induce contact rather than miss bats. That would fit in with the above idea: If he doesn't command the pitch exceptionally well, and leaves it in the wrong spots in the zone too often, hitters are going to benefit rather than ground out meekly to an infielder, or hit a soft fly ball to the outfield.

It doesn't make him a bad pitcher, but let's say Zimmermann continues down the path of his second half, and doesn't rectify things until later in the year, when he begins to use his secondary stuff more effectively. He's likely throwing fewer innings if he's struggling, and the Nationals aren't getting innings of the same quality they are used to.

Then there's Dan Haren, signed to replace Edwin Jackson in the rotation. Haren struggled with back problems that became hip problems during 2012, and while he still managed 176 innings, they were awful ones. His 4.33 ERA might not look that bad, but it came in an extreme pitchers' park in a division with three of those. If healthy, Haren should be a steal for the Nationals, as he averaged a 121 ERA+ from 2009 through 2012, with 234 innings per year. That's a large if, though, as backs can be tricky, and he'll have to recover the lost velocity on his fastball as well. As with Zimmermann, the possibility exists that nothing goes awry, but it's hard to guarantee it given recent history.

The other two rotation members -- Ross Detwiler and Gio Gonzalez -- aren't as concerning, at least in terms of variable outcomes. Gonzalez has shown a similar track record for the past three years, and health has never been much of an issue since he's become a full-time starter in the majors. Bad things could happen, but this is probably the spot that Nationals' fans can be most comfortable with. As for Detwiler, it just has more to do with the fact that he wasn't terribly over his head in 2012. His ERA might jump a bit in the wrong direction, sure, but he wasn't too far off from his career numbers or the expectations created by his minor league numbers and prospect years. The same questions exist for him that do for any young pitcher, and as a contact guy, he can be reliant on a little luck, but he's not an outright concern, especially not as the fifth starter.

Should something happen to any of these arms, though, then it's maybe time to worry. Chris Young, who has managed to throw more than 100 innings in a season exactly twice in the last five years, and combined all of 120 innings in the intervening seasons, is part of the depth. He's home run prone, pitching in a smaller ballpark than he has since 2005, and might not even be around if and when the Nationals could use his services due to a tendency to be injured. Nathan Karns could possibly fill in if needed late in the year, but he has all of 171 professional innings -- all in the minors -- to his credit, and hasn't pitched above High-A yet. Yunesky Maya is an option in an emergency, but the 31-year-old minor-league hurler is not an attractive one, nor is Ross Ohlendorf, who is injured about as often as Young, and has been even less effective as of late.

Depth is not a strength, but the Nationals also might not end up needing it. History says they very well might have to dip into that shallow pool, however, as odds are good at least one of their five plans in the rotation will go awry, and there are notable concerns with a few of those five. It's not something to get into a panic over, but it's worth recognizing, if only to put into context just how special 2012 was for this rotation.

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Marc Normandin writes and edits for Over the Monster, a Boston Red Sox blog, as well as SB Nation's baseball hub. He's one of many behind the e-book "The Hall of Nearly Great," and has written forBaseball Prospectus, ESPN, and others. You can follow him on Twitter at @Marc_Normandin.