KFFL.com's Fantasy Baseball Player Prospecting series highlights the exploits of minor league baseball players, including top MLB prospects. Find out who'll make an impact, whether it's in your rotisserie or head-to-head baseball game next week or in your fantasy baseball keeper league two years from now.

Simmons getting his shot

In what is largely a defensively motivated move, the Atlanta Braves are calling up slick-fielding shortstop Andrelton Simmons from Double-A Mississippi to replace rookie Tyler Pastornicky.

Pastornicky was optioned to Triple-A Gwinnett after hitting .248 with a .605 OPS in 145 at-bats. Pastornicky also posted the lowest fielding percentage (.948) among shortstops in the majors.

In 171 at-bats with Mississippi, Simmons was hitting .292 with three home runs, 21 RBIs, 28 runs scored, a .372 on-base percentage and 10 steals in 12 attempts.

The 22-year-old is a good contact hitter who won the Carolina League batting title with a .311 average last season.

Simmons drew the same amount of walks (20) as strikeouts (20) in Double-A, demonstrating sound improvement in his plate discipline. His walk rate of 10.0 percent this season is leaps and bounds above the 5.1 percent rate he posted in high Single-A last year.

The Curacao native also became a more efficient base stealer this year (83.3 percent) after being successful on only 59 percent of his attempts last year.

While scouts universally acknowledge that Simmons has a chance to be a terrific defender who competes for Gold Gloves someday, there are some doubts about his offensive upside. The big knock against the 6-foot-2, 170-pound shortstop is his lack of home run power.

In time, though, Simmons has shown the ability to develop into a .280-plus hitter at the major league level with 80 runs scored and 20 to 25 steals.

Because of the big jump from Double-A to the majors, Simmons' fantasy impact in 2012 might be limited to an occasional steal, but he has shown this year that he's able to adjust and make improvements on his weaknesses, so he's capable of being a productive fantasy shortstop in time.

Due to his starting status, Simmons is an immediate add in NL-only formats and he has solid keeper value based on his ceiling.

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Just days after Brandon League was temporarily relieved of his closer duties, it didn't take long for the Seattle Mariners to dive into their farm system and promote flame-throwing reliever Stephen Pryor.

Pryor, considered by some to be the Mariners' closer of the future, is expected to be promoted for Friday's game at the Chicago White Sox after the team optioned reliever Steve Delabar to Triple-A Tacoma.

In 28 innings between Double-A and Triple-A this year, Pryor registered a 0.64 ERA, nine saves and a 39:12 strikeout-to-walk ratio. The 6-foot-4, 245-pound right-hander did not allow a home run this year and has only surrendered two homers over the course of 113 career innings in the minors.

Pryor attacks hitters with a mid- to high-90s fastball, a breaking ball and a cutter that he added to his repertoire in the second half of 2011. The 22-year-old's heater has heavy movement and has been clocked as high as 100 mph on the radar gun.

Ever since leaving one of the minors' worst pitching parks in high Single-A High Desert last summer, Pryor has been lights-out on the mound. He registered a 1.18 ERA in 38 2/3 career Double-A frames and did not allow a run during a 12-inning stint in Triple-A.

As evidenced by his career average of 4.6 walks during his career, Pryor does have command issues at times, which is the only real weakness to be concerned about.

For the time being, the M's will likely go with Tom Wilhelmsen, Lucas Luetge or Charlie Furbush to close out games and start off Pryor in a no-pressure, middle-innings role.

There's a lot of speculation that League could be trade bait at the deadline, so showcasing him in the ninth inning could be to their benefit in the next couple of months.

If League is dealt, Wilhelmsen and Pryor are the two relievers in the M's profile that fit the closer profile the best. Based on that, Pryor is worth a speculative add in deep AL-only formats, but most fantasy owners should take a wait-and-see approach.

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Mariners shortstop prospect Nick Franklin has gone on a tear during the month of May, hitting .394 (28-for-71) with 10 doubles, four triples, six steals and a 1.105 OPS with Double-A Jackson.

In 152 at-bats with Jackson, Franklin is batting .342 with two homers, 19 RBIs, 16 runs scored, seven steals and a .945 OPS.

Selected with the 27th overall pick of the 2010 draft, Franklin opened eyes when he swatted 23 homers and stole 25 bases during his first full season of play at low Single-A Clinton in 2010.

However, Franklin was limited to only 88 games last year due to a concussion and an illness, which dropped his home run production down to seven.

The switch-hitter has hit .383 from the left side this year and only a paltry .216 from the right, which falls in line with his averages from a historical standpoint. His lack of success as a right-handed hitter leaves many to believe he will eventually ditch that side altogether.

Franklin projects as an above-average hitting middle infielder who can hit for a good average, swat 15 home runs and steal 20-plus bases in his prime. This season, Franklin has played 29 games at shortstop and nine contests at second base, but most evaluators believe the keystone is his likely destination in the majors.

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1B Jonathan Singleton, the key bat the Houston Astros acquired in the Hunter Pence deal of July 2011, has gone on a home run tear with five round-trippers in his last six games at Double-A Corpus Christi.

The 20-year-old is now batting .316 with 10 home runs, 36 RBIs, 36 runs scored and .988 OPS in 171 at-bats.

The home run surge is very encouraging since scouts have always raved about Singleton's raw power, but he had only shown glimpses of it (13 HR in 2011, 14 HR in 2010) during his teenage years.

With a .396 on-base percentage, Singleton has a strong grasp of the strike zone for his age and overall has shown the makings of developing into an above-average offensive contributor at the major league level.

At the premium hitting position of first base, Singleton's power development will be a key factor in whether he turns out to be a good everyday regular or a perennial All-Star.