It's hard for one player to make that much of a difference over a 162-game season. You'll see several examples this season. A regular player will go down, a reserve will step in, and the team will motor along like nothing happened. A hot streak or two will help cover up for a missing player, or a cold streak or three will make the player's absence the least of the team's worries. Consider the Reds last year, who went 46-27 while Joey Votto was on the DL. That doesn't make any sense. But neither does baseball.
So you can't point at a single player in March and make sweeping proclamations about how important he is to his team. As in, "The Mets are doomed if Lucas Duda can't steal 14 bases!" or "The Marlins don't have much of a chance if Logan Morrison doesn't rebound!" It would be rather silly to get that worked up about a single player.
But every team has a bellwether player, a guy who will be able to serve as a one-man metaphor for how the team's season is going. If the player in question is doing well, there's a good chance that the team's season is going according to plan. If the player is doing poorly, it might mean that everything is in flames for the team. Here, then, are the canaries in the coal mine for each team in baseball, starting with the NL East:
Phillies - Roy Halladay
About that intro, in which I claim that one player doesn't make much of a difference: Roy Halladay was worth about eight wins less in 2012 than he was in either of the previous two seasons. The Halladay of old could have led the Phillies to 89 wins instead of the actual .500 campaign. That would make a big difference in how the team was perceived coming into this season -- the difference between "The Phils just missed the playoffs" and "Good god, the Phillies are old and broken."
There's just about no way Halladay will be worth eight wins again in his career. But he needs to be successful if the Phillies are going to be successful. The Phillies spent their offseason like a team expecting to be competitive, making win-now trades and signing free agents. And laugh all you want at Michael and Delmon Young (no relation), but a front three of Lee/Hamels/Halladay goes a long, long way toward masking other blemishes on the roster.
Lee and Hamels should be fine because they always are. Halladay is the remaining mystery.
Marlins - Jacob Turner
Bad teams have canaries in the coal mine, too. There's no way the Marlins are going to contend this year, but that doesn't mean the team is content to sit back, watch Giancarlo Stanton hit bombs into the teal-and-fuchsia night, and wait for 2016 to roll around. They're looking for progress, for young players to step forward and assert themselves as building blocks. Then they can go into the offseason with a much better idea of what they have, and where they are in the success cycle.
The Marlins have a rotation that starts with Ricky Nolasco and Henderson Alvarez before moving on to Wade LeBlanc. None of these guys will be around for the next good Marlins team. With some poor luck, the Marlins could have guys like Jeff Suppan, Doug Davis or Osvaldo Fernandez in the rotation by the All-Star Break -- stopgaps who really won't be around for the next good Marlins team.
But Turner is supposed to be one of the good ones, maybe the most heralded young player the Marlins acquired in any of the fire-sale moves. And if he's having a breakout year, it'll be hard for the Marlins to complain a lot about how the rest of the season is going. No matter what else happens, if Turner looks like a potential front-of-the-rotation pitcher, the Marlins' rebuilding is probably going well enough at the major-league level. They might not win 60 games, but they'll have 20 percent of the rotation figured out for the next few years.
Nationals - Adam LaRoche
If you wanted to be a cynic, you could really pick apart the Nationals' lineup after the third slot, where Ryan Zimmerman should hit. Jayson Werth will be 34, and his power disappeared last year. Nothing in Ian Desmond's professional career suggests he can sustain the same kind of average and power. Danny Espinosa can't make contact, and Kurt Suzuki is just good enough to steal at-bats from Wilson Ramos, but he isn't very good offensively.
Then there's LaRoche, who was on the scrapheap for a reason last year. He had two lost seasons in a row before his breakout season in 2012. Re-signing LaRoche was one of the key moves of the Nationals' offseason, as it allowed them to trade Mike Morse for prospects and improve the team defense. But is he really as good as he was last year?
Considering how much offense was down around the league, LaRoche had his best season in the majors. It's probably never a good idea to assume an over-30 player can do that again, but if he can, all of that concern-trolling from the first paragraph is probably pointless, and the Nats' offense will be just fine.
Mets - Zack Wheeler
The Mets are probably going to start Marlon Byrd in the outfield, which gives you an example of how much they really care about 2013. Byrd had a -37 OPS+ in the NL last year, though he got it up to 63 in the AL. And they say the AL is the tougher league, after all.
No, the Mets are looking forward, and they're hoping to rebuild their team with young pitching. Matt Harvey was electric last year, and Jon Niese is still just 26. Jenrry Mejia came back from elbow surgery last year, and Noah Synedergaard is one of the better pitching prospects in baseball. There's a foundation there.
Their best prospect, though, is Zack Wheeler. Look at the guy pitch:
I don't care if you've seen it, Giants fans. Look at it again. He's like a composite pitcher created by an ad agency to sell the game of baseball.
He's also a young pitcher. Which means that his arm is still a spider baby trying to avoid being eaten by its own other. He tweaked his oblique already this spring -- a minor tweak that shouldn't keep him from starting the season on time, but any injury is a chilling reminder that prospects will break your heart. A good season for the Mets probably includes Wheeler making the majors and showing the same kind of upside and future dominance that Harvey did last year. A bad season for the Mets would consist of young pitchers doing young-pitcher things, leaving the Mets confused about their direction and short-term future.
Braves - Justin Upton
The Braves' outfield was pretty good last year. Okay, maybe it was better than good: Using Baseball Reference's WAR, it was just the fourth time in history that a team had three outfielders with five wins or more, and the first time since Rickey Henderson's first full season. Before that, Ty Cobb's Tigers did it twice. That's how rare it is to have an outfield have a collective season that spectacular.
But the Braves didn't high-five each other and expect it again. They got greedy. Really, really greedy. Martin Prado probably wasn't going to get much better. Michael Bourn probably wasn't going to get much better. The Uptons, though, have a chance to be much, much better, just based on their youth.
Maybe B.J.'s upside is limited or already known -- he's 28, not exactly an enigmatic player anymore. But Justin is still just 25, and the Braves are chasing his mythical upside, like it's some kind of New World myth from the 16th century. What would Justin's theoretical peak look like? Something from his age-21 season, or something much, much more? For the fourth straight year, the younger Upton's strikeout-to-walk ratio improved. His strikeout rates are much improved from his earlier seasons. All that's missing is the power, which seems to disappear every other year.
If Justin Upton is 75 percent of what he was once expected to be, the Braves will probably enjoy a successful season. If he's the same frustrating player from last season, the Braves will be lamenting the loss of Martin Prado, and wondering why they got so greedy in the first place.