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Having a breakout season is a challenge for most players. Pulling it off in the postseason, when playing time is limited and every next play could potentially determine the season, is another story.

However, every year there are players who do just that, as they go from little-known prospects or under-appreciated veterans to playoff heroes and household names seemingly overnight.

With the playoff games set to begin Tuesday night, it’s time to preview some of the players who appear primed for a breakout performance this October.

Here’s a look at the biggest potential breakout stars for the 2014 postseason.

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The 2014 MLB postseason begins Tuesday, with the Kanas City Royals set to host the Oakland Athletics in the American League Wild Card Game (8:07 p.m. ET, TV: TBS).

Kansas City captured the top AL Wild Card spot to secure its first postseason berth in 29 years, and came within one game of the division-winning Detroit Tigers in the AL Central.

Oakland is returning to the playoffs for the third straight year after finishing one game back of Royals in the Wild Card.

The Royals won the regular-season series against the A’s, 5-2, taking two of three games in Oakland during their first meeting (Aug. 1-3), and then winning three of four at Kauffman Stadium (Aug. 11-14).

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With the regular season coming to an end in a matter of days and the postseason set to begin next week, every playoff team will soon be forced to make difficult decisions regarding its roster.

The number of players a team can roster will drop from the 40 previously allowed in September back to the standard 25 next month. As a result, teams will craft their postseason rosters based on their own strengths as well as the perceived weaknesses of their upcoming opponent.

Many of baseball’s top rookies have a realistic chance of cracking their team’s postseason roster this year, though there will be even more players denied the opportunity to play in October.

Here are five rookies who could carve out huge roles in the 2014 postseason.

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When things get tight at the end of the MLB season, some players show up and guide their teams into the playoffs.

Last season, it was right-hander Michael Wacha, who joined the St. Louis Cardinals starting rotation in early September and subsequently became one of the biggest stories of the postseason, as the rookie took home NLCS MVP honors and pitched his team into the World Series.

Meanwhile, right-hander Gerrit Cole was just as dominant for the Pittsburgh Pirates last season, as the flame-throwing rookie solidified the starting rotation down the stretch and played a major role in his club’s long-overdue postseason berth.

But those are just a couple of unique examples. The reality is that every team fighting for a playoff spot likely has its share of heroes.

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It’s quickly becoming clear why the Boston Red Sox shelled out big bucks last month to sign Cuban outfielder Rusney Castillo.

Castillo connected for his first major league home run in the third inning of Thursday’s 11-1 win over the Tampa Bay Rays, blasting a three-run shot into the seats above the Green Monster in left-center field.

He has continued to showcase his immense potential in the first two games of the weekend series against the rival New York Yankees, going 5-for-6 with a home run and two RBI through Saturday. 

The Red Sox made Castillo the highest-paid Cuban player in baseball history last month, signing the 27-year-old outfielder to a seven-year, $72.5 million contract through the 2020 season.

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This year’s September call-ups’ brief taste of the major leagues might be coming to an end, but it goes without saying that their futures are increasingly bright.

For the better part of the last month, we’ve been highlighting the top call-ups across baseball, whether it be breaking down their early returns in the major leagues or their potential impact on the playoff races.

Today, however, we’re going to look at the very best September call-ups—specifically, prospects that appeared in our recent end-of-year top 100 prospect rankings—by assigning grades for each player’s overall season while also considering how their performances might affect their respective 2015 outlooks.

With all that being said, here are the grades and projections for Major League Baseball’s top September call-ups.

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For the second straight year, the Los Angeles Dodgers are National League West champions.

Led by another strong performance from probable NL Cy Young Award winner and legitimate MVP candidate Clayton Kershaw, the Dodgers trounced the San Francisco Giants 9-1 in front of a sold-out Dodger Stadium to secure home-field advantage in the NLDS.

Though it wasn’t his sharpest outing, Kershaw allowed just one run on eight hits over eight innings in his final start of the regular season, striking out 11 batters without issuing a walk. The win was the left-hander’s 21st of the season, matching his career high from 2011, and he reached the mark in just his 27th start.

Kershaw also helped his cause by going 1-for-2 with an RBI triple, and he made a potentially game-saving play with no outs in the third inning when he fielded a hard-hit, comeback ground ball behind his back to prevent at least one run from scoring.

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Over the last month, Prospect Pipeline has looked at the top prospects for each position at every minor league level and every team’s prospect of the year. We even went so far as to re-rank all 30 farm systems.

But now it’s the time you’ve all been waiting for: an updated ranking of baseball’s top 100 prospects.

For the most part, the placement of the top 25 players is unchanged compared to our most recent update. However, there were numerous prospects (no spoilers!) that shot up the rankings over the course of the season, and many more have entered the ranks in the wake of this year’s amateur draft.

As is the case with all my rankings, any player who’s accrued 130 at-bats or 50 innings in the major leagues no longer qualifies as a prospect. Additionally, I don’t treat international free agents as true prospects, because there’s no benefit in comparing a 26-year-old Cuban player to an 18-year-old draft pick until they log significant stateside experience.

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It will be several years until most of the 2014 draft picks are ready for the major leagues, but that doesn't mean we can’t get excited about the professional debuts of some of baseball’s brightest young players.

Thanks to an accelerated signing deadline in mid-July that was ushered in in 2012 as part of the new collective bargaining agreement—it used to be mid-August—draft picks are now encouraged to quickly begin their professional careers.

For some prospects, signing early gives them a head start on their development as well as the potential to debut in the major leagues ahead of schedule. At the very least, the half-season of experience this summer should improve their chances of receiving aggressive promotions to begin the following season.

Here’s a look at 2014 draft picks who already turned heads in their professional debuts.

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It hasn't even been three weeks since rosters expanded and teams announced their September call-ups, but some of baseball’s top prospects have already made a splash during their short time in the major leagues.

Hitters such as Cory Spangenberg (San Diego Padres), Maikel Franco (Philadelphia Phillies) and Joc Pederson (Los Angeles Dodgers) made immediate impacts with their respective teams to begin the month, but all three players have since cooled down and, in some cases, have had their playing time reduced. 

Beyond that, many of the top pitching-prospect call-ups have opened eyes facing big league hitters for the first time.

The 21-year-old left-handers, Daniel Norris (Toronto Blue Jays) and Brandon Finnegan (Kansas City Royals), both have pitched well in the heat of a playoff race, which is remarkable, considering Norris began the season in the High-A Florida State League, while Finnegan took the mound every Friday night for Texas Christian University.