It has been said it takes 25 men to build a successful season in the Majors. But there are times when it takes the loss of just one player -- often the team's best player -- to tear one down.

Losing a star player for the season or otherwise having that player unable to contribute at a high level is a sure recipe for turning high hopes into a long season.

Now, far be it for anyone to speculate on whether a player may or may not be there for his team -- nobody wants to see that, even the staunchest rival. Nothing's better than beating the bad guys with their biggest, baddest guy right there to enjoy the view and wear the loss.

Let's just say there are guys every team wants to keep very safe, very healthy and perfectly able to do what they do best.

Why? Because the season likely goes down the drain, otherwise.

This is the guy you absolutely need if you're getting there, and everyone knows it.

Everyone knows if you take Albert Pujols out of the Cardinals' lineup, you'd be sure to notice it. Then again, everyone thought the Dodgers would crumble when Manny Ramirez was suspended for 50 games, but players like Andre Ethier and Matt Kemp turned it into an opportunity to shine.

Here are five players from each league who really need to stay healthy and productive for their clubs -- or else:

AMERICAN LEAGUE
Joe Mauer, Twins: Sure, any MVP would be missed. But last year was a great example of Mauer's value. He missed the first month of the season and the Twins went 11-11 in his April absence, but he returned to lead them to the playoffs. A flip side that can't be ignored is that the Twins were without first baseman Justin Morneau down the stretch yet still made it the playoffs. That doesn't mean Morneau isn't valuable -- after all, he was league MVP just three years ago -- but it does illustrate just how stellar Mauer actually is as a double threat, both behind the plate and beside it.

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Mark Teixeira, Yankees: Derek Jeter is the captain, the glue. Alex Rodriguez is the superstar talent. CC Sabathia is a difference-maker, but only every fifth day. Teixeira? The results pretty much speak for themselves. He made a huge difference in the middle of the Yankees' lineup last year, and it could be argued that his powerful switch-hitting presence is really what put the Yankees over the top. He's another April example -- he hit .220, and the Yankees went 12-11. The rest is history.

Ichiro Suzuki, Mariners: For all the moves GM Jack Zduriencik made this offseason and before then, it all comes down to Ichiro, and likely will for the Mariners for as long as he's in Seattle. Ichiro is the rock of the franchise, hands down. No offense to King Felix Hernandez, but this guy's the Emperor. Ichiro needs to perform up to his extraordinary standard for the Mariners to use the influx of talent they acquired this offseason to the fullest. Ichiro went on the DL for the first time to open last year, but he recovered for a ninth straight 200-hit season while earning a ninth Gold Glove.

Jake Peavy, White Sox: OK, so Peavy pitches only every fifth day, just like the aforementioned Sabathia. But this dynamic is a bit different. While Mark Buehrle will get the Opening Day nod, Peavy is the ace the Sox acquired to push their rotation to the top of the league. The linchpin of myriad changes on Chicago's roster over the past year, Peavy is the type of pitcher who delivers quality and intensity every time out. He'll have to do it in a new league on a consistent basis while proving his first real bout with health problems is in the past.

Evan Longoria, Rays: Longoria's arrival was clearly pivotal in 2008, when he immediately contributed to the Rays' magical run to the World Series, jumping right into the Majors at the hot corner and in the middle of the lineup. We haven't seen what the Rays are like without him, and they don't want to see it after he went for 33 homers and 113 RBIs in 157 games last year. The Rays have some weapons, but this one is loaded and proven to be key to their prospects.

NATIONAL LEAGUE
Roy Halladay, Phillies: This guy became the Phillies' key to 2010 the moment he was acquired from Toronto. Halladay's the ace they needed last year, and then some. Cliff Lee carried the heaviest load in the rotation last year after being acquired from Cleveland, and Halladay brings everything Lee brought, and more. Specifically, Halladay brings balance from the right side and an even more impressive track record. All that considered, he needs to be there and be Doc every five days for the Phillies to be on the right track toward a third straight NL pennant.

Yovani Gallardo, Brewers: Another pitcher, and one without a Cy Young resume, Gallardo holds the Brewers' season in his right hand. He's their one standout starter, and it was the breakdown of the rotation that hurt the Brewers down the stretch last year. Without Gallardo, the Brewers have a decent veteran rotation, that's it. With him atop it, the Brewers' rotation has an ace on the rise, with Cy Young potential. Sure, losing either Prince Fielder or Ryan Braun would cause the Brewers serious problems, but at least they'd have the other one to hold down the fort. (See: Pujols-Matt Holliday.) Without Gallardo reaching his potential, the Brewers will have a hard time doing it themselves.

Hanley Ramirez, Marlins: Hanley's uncanny abilities as a five-tool player have helped the Marlins become baseball's overachievers the last two years. He represents a new era for the Marlins, complete with a ballpark of their own in the works for 2012. Signed to a deal through '14, he certainly had a big hand in building it these past few years. There's a lot of young talent on the Marlins, but Hanley is Hanley, and he'd be highly valued -- and therefore missed -- by any team in baseball.

Pablo Sandoval, Giants: The facts are pretty clear: Kung Fu Panda made the biggest difference for the Giants last year, not two-time Cy Young winner Tim Lincecum. Put it this way: The Giants went 72-90 in 2008 and improved to 88-74 in 2009, and Lincecum's Cy Young seasons were quite similar. The biggest difference in '09 was Sandoval, whose presence in the lineup stirred up the Giants and their fans hugely. A switch-hitter who can rake for power and average, Sandoval's season will tell the tale of whether the Giants can break through in the wide-open NL West.

Troy Tulowitzki, Rockies: The proof is very much in the yearly results for Tulo and the Rockies. He absolutely exploded onto the scene in 2007, finishing just two points behind Braun for Rookie of the Year honors, and the Rockies rode the wave to the World Series. Tulowitzki went on the disabled list twice in 2008, missing much of the first half of the season, and both he and the Rockies took a statistical dive. Tulo gets back up with 32 homers, 92 RBIs and 101 runs scored, finishing fifth in MVP voting, and the Rockies are back in the playoffs in 2009. Coincidence? Hardly. The Rockies need Tulo, period.