Breakout prospects who've sent their fantasy stock soaring

The performances of rookies Kris Bryant, Carlos Correa and Miguel Sano are hardly shocking, given that all have been prominent among baseball’s top prospect lists over the past several seasons. But what of the San Francisco Giants’ Matt Duffy, who was on no one’s prospect radar in April but entered Monday batting over .300 with good, hard contact through 437 at-bats? He is challenging Bryant as the National League’s top rookie.

After skipping high A ball, Duffy ran away with the Class AA Eastern League batting title, batting .332 and landing in San Francisco late last season. He held his own with 16 hits in 59 at-bats ( .271 ) in August and September. While Duffy might not have the skills or ceiling of the aforementioned mega prospects, there were season-long signs that he might be better and arrive faster than many observers expected.

Fast-forward to this season. Who are some of the players that, like Duffy in 2014, have surged or seemingly popped up from nowhere? The names below might or might not have been on top-100 lists in March, but after 2015, should receive strong consideration for those in keeper or dynasty leagues. A combination of 2015 performance, overall skills and 2016 opportunity with their current clubs have boosted their fantasy stock as prospects.

Right-hander Alex Reyes of the St. Louis Cardinals had a big arm and two above-average pitches, but with improved conditioning and overall maturation, he is legitimately included as one of the game’s top pitching prospects.

Reyes has posted a 2.53 ERA and struck out 146 hitters in 96 innings between high A and Class AA; he turned 21 in August. His control needs refinement, and a stacked St. Louis rotation means Reyes won’t be rushed. But his elite arm is worth a roster spot, regardless of your keeper league’s depth.

Unlike Reyes, Blake Snell of the Tampa Bay Rays wasn’t on any preseason top-100 lists. But after his 1.33 ERA, plus 157 strikeouts against 50 walks between high A, Class AA and AAA, Snell is being hailed as the American League’s breakout pitching prospect of 2015. The 22-year-old lefty has improved his control (throwing strikes) and command (throwing high-quality strikes), primarily with a solid fastball/changeup combination. He is likely to get a shot at his first extended opportunity in the Rays rotation in 2016.

Snell’s teammate, Taylor Guerrieri, missed much of 2014 and 2015 as he recovered from Tommy John elbow surgery. But the 2011 first-round pick has rebounded nicely, with a 2.06 ERA and a 67/17 strikeout-to-walk (K/BB) ratio with big ground-ball numbers through 70 innings between high A and Class AA.

The Rays are being cautious with Guerrieri because of his early-career inactivity. But his pedigree and combination of stuff and command suggest he could move fast.

Infielder Chad Pinder of the Oakland Athletics might be the closest thing to Duffy on our list, in that he has never been a highly rated prospect. In addition, his lack of plate patience doesn’t remind us of most Oakland prospects. But all Pinder has done at Class AA this season is make loud contact, as suggested by a .346 average and nine home runs in 286 at-bats since May.

Fighting for a Texas League batting title, Pinder could get strong consideration for the A’s long-standing second-base hole as early as next season.

A terrific athlete, Toronto Blue Jays outfielder Anthony Alford is finishing his first full-time professional baseball season after spending most of three seasons playing college football. The results have been impressive.

Alford, 21, is flirting with a .300 average while showing excellent plate patience (63 walks in 389 at-bats) and defense along with a rapidly improving running game (25 steals) across Class A and high A. While he’s likely at least a year away from the big leagues, Alford is showing elite top-of-the-lineup skills. And more than a few analysts think his hitting ability and power will jump with more experience in 2016.

For keeper league owners planning for the long term, no offensive prospect has produced more late-season chatter than Washington Nationals outfielder Victor Robles, 18. He has spent 2015 in the low minors, where he has hit .348 with a .442 on-base percentage and .519 slugging percentage, to go with 19 steals in 187 at-bats.

He’s a long way from his big-league debut, but Robles’ contact, plate skills, excellent speed, athleticism and instincts have drawn raves from everyone who has watched him. More than a few analysts have projected above-average power as Robles’ body fills out. For win-now owners, the buzz surrounding Robles makes him a viable trade chip as early as March.

The pitching equivalent of Robles is 17-year-old Anderson Espinoza of the Boston Red Sox. Armed with high-90s velocity, good breaking stuff and a developing changeup, Espinoza has put up an 0.82 ERA in the low minors, accompanied by a 61/12 K/BB and a heavy ground-ball lean. Though he’s years away from Boston, the “unlimited-upside” tag that scouts and analysts have hung on Espinoza should perk up the ears of any keeper/dynasty league owner.

Milwaukee Brewers shortstop Orlando Arcia, 20, has impressed with a line of .307/.347/.459 (batting average/on-base percentage/slugging percentage) in Class AA. Defense is his biggest draw, and he won’t approach Correa’s elite offensive ceiling. But he has plenty of room for development and likely will debut in 2016.

Minnesota Twins prospect Max Kepler has had a huge breakout season. Signed out of Germany in 2009, athletic Kepler was unable to hit for average or power over his first four professional seasons, despite solid plate skills. But in his first exposure to Class AA, healthier Kepler has become a force, producing a .330/.416/.545 line and leading the Southern League in batting. Despite just nine home runs, Kepler’s solid contact and speed have produced 53 extra-base hits along with 17 steals. His 1-1 walk-to-strikeout ratio, along with his imposing 6-4, 200-pound frame, give Kepler remaining power projection.

If it’s major league-ready power you seek, look no further than Rays 1B-DH Richie Shaffer, who has hit 26 home runs in the minors this season. Despite plenty of swing-and-miss to his game, which reduces his batting average potential, Shaffer has 54 walks, indicating he’s more than just an undisciplined hacker. He’ll get more major league at-bats during September roster expansion as well as plenty of 2016 playing-time consideration for the offense-needy Rays.