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The Arizona Diamondbacks made a splash this offseason with the high-profile signing of Cuban outfielder/third baseman Yasmany Tomas, the biggest name on the international market.

Tomas, 24, inked a four-year deal worth $68.5 million, making him the second-highest-paid Cuban player in baseball behind Boston’s Rusney Castillo.

Naturally, there are high expectations for Tomas, who is making the jump directly to the major leagues and being asked to play a new position (we’ll get to that in a bit).

Given the number of Cuban players to make an impact in recent years—and there are more on the way after Tuesday’s news that MLB has adjusted the signing process for Cuban players—and the money saved on their contracts through team-friendly deals, all signs point to Tomas becoming a star player in the big leagues. Right?

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Not every successful major league player is a former top prospect. Typically, it’s the high-profile, high-ceiling players who typically garner the most hype as they ascend the organizational ladder.

One of the more rewarding aspects of scouting is identifying young players who, despite flying under the radar or underperforming early in their careers, have considerable room for improvement and showcase the potential to be impact players in the major leagues.

With that being said, here’s a look at seven prospects who will improve the most in 2015.

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Major League Baseball’s offseason is winding down, and before we know it pitchers and catchers will start reporting for spring training.

With that timeline in mind, most general managers are still trying to plug holes on their respective rosters or at least build depth in anticipation of position battles during spring training.

Teams are usually reluctant to break camp with young, inexperienced prospects on the big league roster—especially if they’re not already on the 40-man roster. Instead, they prefer to send them to Double- or Triple-A for a few more months of seasoning and to avoid an extra year of arbitration down the road.

However, there are numerous prospects who will have an opportunity to make an Opening Day roster in 2015, if all goes as planned, and spend the entire season in the major leagues.

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It’s never too early to start looking at the MLB draft.

This year's class is especially deep on the mound, with college pitchers such as right-hander Mike Matuella (Duke), right-hander Kyle Funkhouser (Louisville), righty Walker Buehler (Vanderbilt) and left-hander Nathan Kirby (Virginia) expected to come off the board early in the first round. Prep left-handers Brady Aiken, Kolby Allard and Justin Hooper are also in the mix.

However, impact hitters once again are few and far between in this year's class, as shortstop Brendan Rodgers and middle infielder Dansby Swanson (Vanderbilt) represent the top prep and college bats, respectively, and will likely be selected within the top 10 picks.

But with that said, endless changes are guaranteed in the class’ player rankings between now and June, as countless names will fall out of consideration and be replaced by other up-and-coming draft prospects.

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The signing of free agent Max Scherzer to a seven-year, $210 million contract improved the Washington Nationals’ starting rotation from arguably the best to undoubtedly the best in baseball.

The Nats will enter the 2015 season with three No. 1 starters in Scherzer, Jordan Zimmermann and Stephen Strasburg, with Gio Gonzalez, Doug Fister and Tanner Roark “filling out” the staff. However, the Scherzer signing also led to speculation that the Nats now might be more inclined to trade from their pitching depth.

Jon Morosi of Fox Sports tweeted that Washington would be willing to deal either Zimmermann or Strasburg if they landed Scherzer, which makes sense, as Zimmermann is set to become a free agent after the 2015 season and likely to command a monster free-agent contract, while Strasburg is set to follow in his footsteps the following year.

But there’s one other major reason the Nationals seemingly are willing to consider dealing young talents such as Zimmermann and Strasburg: They have baseball’s top pitching prospect in 20-year-old right-hander Lucas Giolito.

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Earlier today Prospect Pipeline completed our rankings of every organization’s top-10 prospects for the 2015 season. Now, it's now time to go back and break down every club's No. 1 prospect in the form of a team-by-team ranking.

In preparation for spring training as well as our official list of the top 100 prospects for the upcoming season, we’ve put together a tentative ranking of each team's best prospect heading into 2015. Some of the scouting notes for each player have been derived from his original scouting report.

Here are our rankings of the top prospect for all 30 MLB teams entering 2015.

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It was widely believed that top prospect Archie Bradley would spend most of the 2014 season in the major leagues, but an elbow injury in late April cut into his development and forced the organization to reassess his timeline. The right-hander looked better in this year’s Arizona Fall League, but he'll still have some questions to answer in the upcoming season.

Braden Shipley, the No. 15 pick in last year's draft, proved to be a first-round steal with a plus fastball-changeup combination, impressive athleticism and better than expected command. The team’s Compensation Round A pick from last year, right-hander Aaron Blair, has also been impressive this season, as he dominated at three levels, including Double-A.

The Diamondbacks landed another potential steal this year when Touki Toussaint fell in their lap at No. 16 overall, followed by ultra-athletic outfielder Marcus Wilson in compensation round B.

22-year-old Brandon Drury, who was acquired from the Braves in the Justin Upton deal, has a good eye at the plate, makes a lot of contact and has grown into some power. The same applies to 243-year-old third baseman Jake Lamb, who received a promotion to the major leagues in August after raking at Double-A Mobile.

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Major League Baseball is being dominated by pitching, and that's only going to continue, judging by the flood of elite young arms who are on the verge of reaching The Show.

Like these 10, who represent the sport's can't-miss pitching prospects for the 2015 season.

To avoid any confusion, that means these pitchers should be making a major impact in the upcoming year.

Thus, you won't see elite arms like Lucas Giolito of the Washington Nationals, Tyler Glasnow of the Pittsburgh Pirates or Luis Severino of the New York Yankees, all of whom are a bit too far away to take the majors by storm this year. Same goes for 18-year-old Los Angeles Dodgers phenom Julio Urias.

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While the San Francisco Giants’ system is top-heavy with pitching prospects, many of the organization’s top young arms profile as either back-end-starter types or guys who might not throw enough strikes to even stick in the rotation.

Right-hander Kyle Crick, 22, might have the highest ceiling in the system, but both his control and command were a mess last season in the Eastern League. Clayton Blackburn, another right-hander, has the highest probability to reach his projected ceiling in the big leagues, as he has good command of a four-pitch mix to go along with a feel for sequencing. 

Ty Blach, 23, is basically a left-handed version of Blackburn, as he lacks overpowering stuff but features advanced command of three pitches. And don’t sleep on hard-throwing right-hander Keury Mella, who's right there with Crick in the conversation for most upside.

The Giants went after Vanderbilt righty Tyler Beede in the first round (No. 14 overall) of the draft, and, unfortunately, his lack of control/command puts him in the same boat as Crick. However, based on what Crick hasn’t accomplished over the past two seasons, I’d give Beede better odds of reaching his potential.

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If case you haven’t been paying attention, the San Diego Padres and first-time general manager A.J. Preller have been busy this offseason.

Since the beginning of December, the Padres have added some of baseball’s premier right-handed power hitters through trades in outfielders Justin Upton, Matt Kemp and Wil Myers, as well as catcher Derek Norris.

Amazingly, Preller was able to acquire the aforementioned players without giving up the organization’s three best prospects. However, that’s not to say the club didn’t part with a vast collection of promising young players: SS Trea Turner (will officially be traded in mid-June), LHP Max Fried, RHP Zach Eflin, RHP Joe Ross, RHP Joe Wieland, RHP Burch Smith, CF Mallex Smith, INF Jace Peterson, RHP R.J. Alvarez, 1B Jake Bauers and 3B Dustin Peterson.

Austin Hedges is still one of the better catching prospect in baseball thanks to his elite defensive chops, but his bat dragged behind the rest of his game this past season at Double-A San Antonio.