Gabriel Guerrero, OF, Mariners (High-A High Desert)

It’s well-established that this Guerrero is the nephew of that Guerrero, just as it’s established that this Guerrero first tickled my fancy during spring training of 2013 and continues to tantalize my emotions based on characteristics shared with that Guerrero. After a slow start last-season—his first in a cold-weather environment—Gabby Guerrero’s bat warmed up as the climate did the same, and he positioned himself to take another step forward with a starting assignment in the hitter-friendly environments of the California League in 2014. The 20-year-old Dominican has one of the loosest and easiest swings around, with plenty of bat speed and natural lift designed to drive the baseball into the gaps and over the fence. He runs into trouble against arm-side stuff, and his pitch recognition could end up being a bigger issue than his early stat-line might indicate. Guerrero has such tremendous hand/eye coordination and bat speed that he can often recover against bad guesses or late recognition, but as he climbs the chain, better pitching is likely to expose these weaknesses and limit his impact potential. As much as I love to watch this Guerrero swing—as the physical body, the sans batting glove swagger, and the looseness in the swing all remind me of that Guerrero—I’m hesitant to buy into the statistical success out of fear of the scouting reality. For me, this Guerrero is still very much a boom-or-bust prospect, and I’m unlikely to find comfort in his progress until he finds success at the Double-A level. —Jason Parks

Preston Tucker, OF, Astros (Double-A Corpus Christi)

Preston Tucker can hit. He’s a below-average athlete with below-average speed and average arm utility, but the 23-year-old excels at the skill that matters the most for a position player: bat-to-ball. It’s a strong, short-to-the-ball swing that is built for loud contact and solid power. He’s not an all-world type and he’s unlikely to develop into a first-division player, despite the ability to strike right-handed pitching. But the former seventh-round pick from the University of Florida is a much better prospect than people realize, and it's all tied to his natural ability to put his bat on a baseball and drive it with authority. At the highest level, Tucker is probably a fringe-average corner defender, with his below-average speed and average arm likely pushing him to left field, which will put all the pressure on his bat to carve out the value. But if the hit tool plays to potential, it’s realistic to envision a future .275-plus hitter with 15– to 20–home run potential. Not a guy who will change the fortune of a franchise, but a cost-effective player who can contribute to a major league line-up. The Astros will take that all day long with a smile. —Jason Parks

Julio Urias, LHP, Dodgers (High-A Rancho Cucamonga)

When watching Urias take the hill, it’s easy to forget that the left-handed starter is just 17 years old. Whether it’s the ball easily coming out of his hand at 93 to 95 mph, the crispness of the delivery, the sharpness of the secondary stuff or just the overall level of polish, Urias’ package is advanced beyond his years. I was thoroughly impressed with the lefty when seeing him during spring training, recognizing that he has a chance to develop into an impact player down the road.

While the shine of Urias’ advancement is almost blinding, it’s also important to put into context the amount of development in front of him, mainly with building stamina and overall experience. He logged just 54 1/3 innings last season over 18 starts. The goal this year will be to add innings and continue to stretch out. That’s not to say that he can’t push a promotion during the season, but keep in mind that, at 17, he is in the infancy stages of ramping up physically. A successful year is getting over 100 innings. —Chris Mellen

Christian Vazquez, C, Red Sox (Triple-A Pawtucket)

Vazquez has come a long way since first signing as a pro. Though the body still leaves a bit to be desired, the 23-year-old has made leaps and bounds with his overall game, especially on defense. Vazquez’s pop times routinely clock in the 1.8s, with the arm grading as plus-plus. His feet have gone from tangled and messy to crisp and extremely fluid. I think back to when I saw him in those early stages and I didn’t see much more than an organizational player. Now, he’s on the cusp of the bigs.

Vazquez is a good example of how a prospect can transform over the course of his development. While he is more the exception than the norm, his progression highlights the variety of the process. I don’t see Vazquez making a big impact with the bat. It’s likely to be on the modest side. The real impact can be with the glove, and can carry him to a role as a regular in the right situation. The defense can push well above average. Though loud tools and high ceilings grab most of the attention, Vazquez has the potential to carve out a long career and provide good value to a roster. —Chris Mellen

Samuel Tuivailala, RHP, Cardinals (High-A Palm Beach)

If at first glance Tuivailala looks like a converted position player, it's because he is. He took to the mound in 2012 after failing as a shortstop and has been striking out large numbers of batters ever since. Tuivailala does so with premium velocity. He sits comfortably from 94 to 95 mph with his fastball and can reach back and touch 97. It's straight, but his 6-foot-3 frame helps him create a good downward plane. He has little command to this point, and struggles to throw strikes, a testament to his limited time on the mound. The only hint of an off-speed pitch is a slider that he throws between 79 and 81 mph. It has some potential with a bit of hard bite and tilt, but he struggles to command it at all. There is little interest in anything off-speed, so he'll need to develop something to combat left-handed batters. With a quick-twitch arm and mechanics that he repeats well, he should be able to get his control to a respectable enough level. If he can develop an average secondary pitch and average command of his fastball, his velocity will be enough to carry him into a major league bullpen role. —Jeff Moore

Javier Betancourt, 2B, Tigers (Low-A West Michigan)

Betancourt had generated some hype with a strong showing in the GCL and was listed as an On The Rise candidate in the Tigers system this year. I had the chance to watch 15 or so plate appearances on the backfields in Florida and came away unbelievably impressed. It took only one time at the plate for me to tell that he approaches the game differently than most prospects. Betancourt has a calm, collected approach, and you can tell that the game naturally slows down for him. He has impeccable instincts all around and doesn't look like an ordinary 18-year-old on the diamond. Growing up around baseball as Edgardo Alfonso's nephew doesn't hurt.

At bat, Betancourt does an outstanding job of staying balanced, and even his takes are impressive. His bat stays flat through the hitting zone for a long time, and he barrels balls all over the yard. So far, Betancourt is leading the Midwest League in hits even though he doesn't turn 19 for another few weeks. He doesn't possess much current power, but as he gets a bit stronger, it will play: His line drives have a lot of topspin right now. In the field, Betancourt looks to have all the tools to be a solid-average second baseman in the majors, with an excellent IQ, average range, and average arm. In a thin system, Betancourt looks to have locked up a spot in the future Tigers Top 10. —Jordan Gorosh

D.J. Peterson, 3B/1B, Mariners (High-A High Desert)

Peterson is a physical presence on the field—listed at 6-foot-1 and 190 pounds, he appears closer to 220—and oozes major league qualities that you don’t see from most of his peers in the Cal League. He took batting practice with a plan, lining the ball the opposite way and going up the middle with regularity. The last session, he put multiple balls out of the park to his pull side and one to dead center at least 420 feet away. The raw power is well above average and I looked forward to seeing the utility of that tool put on display during game action. Unfortunately, Peterson pressed at the plate in the two games I saw, with poor pitch recognition and an aggressive approach that put him behind in the count more often than not. He was out on his front foot and off-balance against arm-side spin on multiple occasions, which saps him of his bat speed and strength, his carrying tools. However, he was able to spit on some close pitches in the second game and net a couple of clean singles. There’s always going to be swing-and-miss in his game because of his aggressiveness; whether that’s simply anxiety to get going this season or a major character flaw we’ll find out when summer months approach. —Chris Rodriguez

Corey Seager, SS, Dodgers (Rancho Cucamonga)

When it comes to evaluating shortstop prospects with big frames, one of the toughest questions a scout must answer is whether that player can stick at the position. Prospects on the fast track to the major leagues may be able to hold down shortstop in the short term, since their bodies may not fully mature until later in their careers. Seager, however, may not fit that mold. The 19-year-old is filling out his large frame at a rapid pace, which will force him to move to third base sooner rather than later. But Seager will be known for his bat, which could help propel him into a star at the highest level. He shows developing over-the-fence power in batting practice and during games, creating tons of backspin. I was most impressed by his mental approach to hitting, stepping into the batter’s box with a patient, selective plan in every plate appearance. It isn’t all roses, though, as Seager still needs to work on the little things. After hitting a high fly to left field, Seager didn’t take a step out of the box until it had landed in fair territory between two oncoming defenders. Just about any runner would have ended up on second base, but he had to scramble to make it to first. Nonetheless, maturation should come in due time while Seager works on converting his tools into baseball skills. —Ron Shah

Kris Bryant, 3B, Cubs (Double-A Tennessee)

Bryant entered the 2014 season as the 17th-best prospect in the game and the no. 2 prospect in the Cubs system, his lofty status fueled by elite raw power and a projected hit tool that some feel could dovetail with the pop at about a grade-and-a-half discount (still above average). The primary barrier to Bryant reaching his elite offensive upside, and the aspect of his game being watched most closely, is a lengthy swing that could see the swing-and-miss in his game creep higher as he begins to tackle more advanced arms. Through 60 Double-A plate appearances in 2014, these concerns have not abated, as Bryant continues to strike out about once every four trips. The whiffs haven’t limited the playable pop yet (slugging .617) and he continues to take professional at-bats showing an advanced feel for the strike zone (walking in around 16 percent of his plate appearances and making lots of hard contact), but the competition is only getting better and Bryant’s ability to start making adjustments will be key to his future offensive development. If he can close the holes in his plate coverage, we could see a huge jump in production in short order, as well as a late-2014 cup of coffee in Wrigley. —Nick J. Faleris

Tyrone Taylor, OF, Brewers (High-A Brevard County)

At a young 20 years old, Taylor’s presence at High-A is a testament to the progress he has made through his season-plus of professional ball. The former second-rounder continues to see positive growth in his defensive play to the point where it is getting easy to picture him as a plus defender up the middle, with his decision-making, including routes, becoming more and more instinctual as his feel for the craft grows. At the plate Taylor is generally putting together solid at-bats, though this past week has seen him start to press, resulting in expanding the zone and giving away at-bats. Even with a rough week, the Brewers’ top prospect is already showing easier access to his power tool in-game than he showed last summer, notching ten doubles in his first thirteen games and adding his first home run of the season on Saturday. Taylor is certain to have ups and downs in 2014, but if he can hold his own as a 20-year-old in High-A—flashing his leather in center and increasing his in-game power output—the season will be an unmitigated success. —Nick J. Faleris

Brady Aiken, LHP, Cardiff by the Sea, CA HS

Aiken has been on the 2014 draft radar for as long as that radar has existed. At this time a year ago he was seen as one of the top high school left-handers, with a likely starter profile and the potential for at least three average or better pitches and a chance to command them. That had him in the discussion to potentially become a first-round pick, but he wasn't squarely ensconced in the conversation for the top of that round.

When the calendar flipped to 2014, Aiken emphatically announced his candidacy for the top five picks by reportedly touching 97 mph in a heavily scouted one inning stint against fellow first-rounder Alex Jackson. In his most recent outing he worked in the 90-94 range and backed it with two secondary pitches that showed plus potential, with an upper-70s curveball and a mid-80s changeup.

It was widely assumed by many media outlets that the Astros had already made up their mind that NC State lefty Carlos Rodon would be their choice for the first overall pick. As the spring has progressed, Rodon has reportedly struggled to maintain the same high-level velocity that he showed as a sophomore last season, leading to rampant speculation as to who Houston will tab with the first pick. Against that backdrop, Aiken's progress has not only put him in the mix for the top five, but has at least worked him into the conversation for the 1/1 pick.

In hindsight, the across-the-board development that Aiken has shown should have been obvious. The increased power to each of his three pitches is directly in line with the developmental progress he showed in the preceding years of his high school career. He always showed relatively advanced command and feel for an underclassman, and that hasn't changed as he's improved the quality of his stuff. Thus, the 17-year-old lefty now possesses the kind of well-commanded three pitch arsenal that is typically found in the college ranks.â€‹ —Todd Gold