Talent and opportunity aren't the only factors that dictate when a team calls up a prospect. Service-time considerations also play a role.
A player needs six full years of service time to reach free agency, so clubs will sometimes delay promotions a couple weeks at the start of the season. The most famous recent example of this came in 2015, when Kristopher Bryant led all players with nine homers during Spring Training yet the Cubs waited until April 17 to summon him from Triple-A. As a result, he'll become a free agent after the 2021 season rather than after 2020.
The arbitration cutoff is more difficult to pinpoint. All players with three years of service time qualify, but so do the top 22 percent of players with between two and three years who spent at least half of the previous season in the big leagues. The number of days required to join that latter group, commonly referred to as Super Two players, fluctuates from year to year.
In general, if a team waits until early June to promote a prospect, it can avoid Super Two repercussions. It's not entirely coincidental that four of MLBPipeline.com's Top 100 Prospects were brought to the Majors for the first time in the last couple of weeks: Astros right-hander Francis Martes (June 8), Braves left-hander Sean Newcomb (June 10), Astros outfielder Derek Fisher (June 14) and Athletics third baseman Matt Chapman (June 15). Houston returned Fisher to Triple-A on Wednesday.
Which other Top 100 Prospects are performing well enough to merit callups now that their teams don't have to sweat Super Two status? Here's a baker's dozen of candidates:
Yoan Moncada, 2B, White Sox (No. 1 on Top 100)
He accrued 31 days of service time after a September callup with the Red Sox last year, so Chicago will want to wait a little while longer on the prize of the Chris Sale trade. He's hitting .282/.387/.432 with 14 steals at Triple-A, though his strikeout rate is still high at 28 percent.

Amed Rosario, SS, Mets (No. 3)
There's not much left for him to prove in Triple-A, where he's batting .325/.368/.479 with 12 steals. Rosario also would give New York a huge defensive upgrade over Asdrubal Cabrera and Jose Reyes.
Ozzie Albies, 2B, Braves (No. 7)
He's doing what he always does, hitting for average (.273/.324/.420 in Triple-A) and stealing bases (18 steals, second in the International League) as one of the youngest regulars in his circuit (age 20). If Atlanta deals Brandon Phillips, Albies could be his immediate replacement.

Rafael Devers, 3B, Red Sox (No. 12)
The Red Sox' plan wasn't to call him up this year, but they have to start considering the move because third base is a huge problem in Boston. The youngest regular (age 20) in the Double-A Eastern League, he's batting .297/.355/.569 with 14 homers.
Willy Adames, SS, Rays (No. 16)
Though former No. 1 overall pick Timothy Beckham is playing well at shortstop, Adames has a brighter future and also could do a better job at second base, where Daniel Robertson is filling in for an injured Brad Miller. He's hitting .270/.360/.403 in his first taste of Triple-A.
Clint Frazier, OF, Yankees (No. 18)
For now, he's blocked by Brett Gardner, Aaron Hicks and Aaron Judge, who are helping fuel one of the most productive lineups in the big leagues. Frazier scuffled when he got to Triple-A last year, but has adjusted nicely in 2017, batting .254/.344/.484 with 12 homers.

Brent Honeywell, RHP, Rays (No. 24)
Rookie Jacob Faria has been lights out since arriving in Tampa Bay, but Erasmo Ramirez has been a weak link at the end of the rotation. Though Honeywell has gotten hit harder than usual since getting to Triple-A (4.91 ERA, .295 opponent average), he's still missing bats with multiple pitches and filling the strike zone (74/14 K/BB in 62 1/3 innings).
Carson Kelly, C, Cardinals (No. 34)
St. Louis isn't looking to displace Yadier Molina, but Kelly could give the 34-year-old some extra rest and he offers much more than current backup Eric Fryer. Kelly is providing excellent defense as always and batting .292/.382/.466 in Triple-A. He did earn 29 days of service time last September.
Francisco Mejia, C, Indians (No. 35)
Kelly's rival as baseball's best catching prospect, he's batting .366/.410/.611 in Double-A and topping the Eastern League in hitting and slugging a year after setting a modern Minor League record with a 50-game hitting streak. He also owns a cannon arm, and while he hasn't set foot in Triple-A, Yan Gomes and Roberto Perez are struggling in Cleveland.

Reynaldo Lopez, RHP, White Sox (No. 38)
He amassed 44 days of service time with the Nationals last year before becoming part of the Adam Eaton trade, so Chicago may hold off a little longer on Lopez. He's 5-3 with a 3.91 ERA and 64 strikeouts in 71 1/3 Triple-A innings, and he may continue to refine his control at that level until the White Sox shed veterans at the Trade Deadline.
Nick Gordon, SS, Twins (No. 42)
Minnesota is a surprise contender despite getting little offense out of Jorge Polanco. While Gordon has yet to play above Double-A, he's batting .315/.376/.504 and wouldn't be daunted by skipping a level.
Franklin Barreto, SS, Athletics (No. 44)
Adam Rosales isn't a part of Oakland's future and looks cooked at age 34. Barreto is a superior hitter and defender who's batting .279/.321/.431 in Triple-A, albeit with a Pacific Coast League-high 89 strikeouts.
Yohander Mendez, LHP, Rangers (No. 48)
Yu Darvish has been the lone healthy and effective starter in Texas, which could turn to Mendez, a September 2016 callup with 31 days of service time. He lives in the strike zone and has one of the better changeups in the Minors, which has helped him go 5-4 with a 3.48 ERA, 71 strikeouts and a .206 opponent average in 88 Double-A innings.