An estimated 100 players have left Cuba in search of a Major League contract in the past 12 months.
How many of those players will sign with a big league club is up for debate. What's certain is that the once powerful Serie Nacional, the island's top league, has been depleted by the defections from its top players over the past few years. Not surprisingly, many of the recent players to leave Cuba are much younger than their predecessors, so they are subject to international signing guidelines because of their age and experience.
Yaisel Sierra, 24, is the exception. The right-handed pitcher is considered the top unrestricted free agent from Cuba available this offseason, and he could sign once he is declared a free agent.
Some scouts think Sierra can be a top-of-the-rotation pitcher. Others think he might be best suited for the middle of the rotation and that he needs to work on his command. Sierra's fastball was in the 94-97-mph range consistently, and he hit 98 mph in a showcase in front of 100 scouts in August in the Dominican Republic.
Sierra also shined in three innings during a showcase at Roger Dean Stadium in Jupiter, Fla., in front of an estimated 350 scouts on Oct. 23. He has also been throwing for teams each week for the past two months in the Dominican Republic. Because of Sierra's age and experience, he will not be subject to the international signing guidelines.
There's a belief that Sierra can help a Major League team next season. He could also command a contract comparable to the seven-year, $27 million deal the Reds gave to Cuban starting pitcher Raisel Iglesias last summer and the four-year, $32 million deal starter Jose Contreras signed with the Yankees in 2002.
Joining Sierra on the list of top unrestricted free agents from Cuba available are outfielder Guillermo Heredia, infielders Luis Yander La O Camacho and Pavel Quesada. Pitcher Vladimir Gutierrez, outfielder Yusniel Diaz along with pitcher Norge Ruiz, Cionel Perez and Adrian Morejon headline a long list of young prospects from Cuba subject to the international signing guidelines. Most of these players are in various stages of their paperwork to become eligible to sign.
The Cubs, Dodgers, Giants and Royals -- who will not be able to sign any pool-eligible prospects for more than $300,000 for the next two international signing periods after exceeding their bonus pools this year -- are still in play for players eligible to sign under the international guidelines. The Angels, D-backs, Rays, Red Sox and Yankees are already in the maximum penalty after blowing past their bonus pools last year.
Video: Yaisel Sierra pitches well at the WWBA Championship
Other unrestricted free agents from Cuba to watch
Guillermo Heredia, 24, OF
The starting center fielder for Cuba during the 2013 World Baseball Classic, trained with pitcher Vladimir Gutierrez in Mexico and joined him at a showcase in Delray Beach, Fla., last month. The 5-foot-11, 180-pound Heredia ran a 6.4-second 60-yard dash during the showcase and showed line-drive power during batting practice. He displayed an average arm and hit from both sides of the plate. He is best known for his speed and defensive skills.
Heredia is free to sign.
Luis Yander La O Camacho, 23, INF
Camacho, who played six seasons for Santiago de Cuba in Serie Nacional, will not be subject to the international signing guidelines because of his age and experience when he is declared a free agent.
An established hitter, Camacho posted a .312 batting average with eight home runs and 113 RBIs in his career in Cuba. He hit .325 with two home runs and 39 RBIs in 76 games for Santiago and Matanzas during the 2014-15 season.
The infielder was a key player for Cuba's 2015 Caribbean Series championship team in Puerto Rico, picking up seven hits in 16 at-bats with two runs and one RBI in four games.
Pavel Quesada, 27, 2B/3B
Known as a plus-hitter, Quesada once starred in the same Cienfuegos infield as Erisbel Arruebarrena, Yoan Moncada and Jose Abreu in Cuba, but he has obviously not reached their level of success. The long layoff -- he resigned from his Cuban team and did not play for six months -- left Quesada out of shape and in poor condition for showcases when he arrived late in the summer of 2014. Scouts were not impressed with the plump Quesada.
Quesada now works out twice each day and has lost 30 pounds in the past five months. He's once again become an intriguing option for curious scouts. Quesada is free to sign.
More unrestricted free agents from Cuba to watch: Utility player Maikel Caseres Dorsine; outfielders Yadiel Hernandez, Yanio Luis Perez, Yusnier Aguilar, Ramon Lunar and Joaquin Carbonell; left-handed pitcher Pedro Duran; right-handed pitchers Jorge Despaigne and Jorge Luis Bravo Ramirez; and catcher Lorenzo Quintana.
Because these players are not at least 23 years old with at least five years of experience in Cuba's Serie Nacional, they will be subject to the international signing guidelines, usually referred to as the July 2 signing period rules.
Vladimir Gutierrez, 19, RHP
Gutierrez is free to sign, but continues to work out for teams and might not sign until after the Winter Meetings in Nashville, Tenn., next month.
Gutierrez threw two innings in front of 120 scouts at a showcase with outfielder Guillermo Heredia on Oct. 24 at the Elev8 Baseball Academy in Delray Beach, Fla. His fastball was clocked in the 89-92-mph range and he topped out at 94 mph at the showcase. Gutierrez showed a decent curveball and changeup, but he didn't display his best command.
The 6-foot-3, 172-pound Gutierrez was the Serie Nacional Rookie of the Year during the 2013-14 season. He went 5-5 with a 3.90 ERA during his rookie season, primarily pitching out of the bullpen. Gutierrez also sported a 2.45 ERA as a reliever during the 2014-15 season. The pitcher left his Pinar del Rio team during the Caribbean Series in February in San Juan, Puerto Rico, and made his way to Mexico, where he eventually established residency in May.
Yusniel Diaz, 19, OF
The 6-foot-1, 185-pound Diaz is free to sign and has been a main attraction at private workouts and showcases in the Dominican Republic since early August.
Diaz continues to show athleticism along with some hitting and power potential in the showcases. He has clocked sub-6.5-second 60-yard dashes and also impressed scouts with his body projection. Evaluators also liked Diaz's bat speed and believe he can play center field.
Norge Ruiz, 21, RHP
Ruiz has been described as a bulldog that lives in the strike zone. He has three quality pitches: fastball, changeup and curveball. Ruiz is more of finesse pitcher with a fastball that hovers in the 89-93-mph range. He has not been declared a free agent.
Cionel Perez, 19, LHP
The 5-foot-10, 150-pounder has a fastball that hovers in the 89-93-mph range. Perez tops out around 95 mph and has touched 96 mph. He is learning "a feel" for his changeup and slider. Perez is an intriguing option because of his tools and ability, although it's unclear if he will be a starter or a reliever. He has not been declared a free agent.
Adrian Morejon, 16, LHP
Morejon is the real deal. The left-handed teenager has shined in international competitions, and his fastball hovers in the 91-93 mph range. Morejon has four pitches, plus command and plus makeup. He's an international star and one scout said he might be the best young arm overall in 2016, and that includes the international market and the 2016 Draft. Morejon is working on his documents and has not been declared a free agent.
Jorge Oña, 19, OF
The 6-foot-1, 215-pound teenager has a good approach at the plate for a player his age and has been clocked at 6.85 in the 60-yard dash. Oña is big and solid, with a nice simple swing and raw power. He has not been declared a free agent.
Lazarito Armenteros, 16, OF
The 6-foot-2, 205-pound Armenteros was named to the all-tournament team after hitting .462 with nine runs, three doubles, five triples and eight RBIs in nine games during Cuba's championship run at the U15 Baseball World Cup in Mexico last year.
Armenteros also had 42 hits in 38 games, with eight doubles, three triples, six home runs and 12 stolen bases for Havana's under-15 team in 2014. He recorded five hits, including two triples, in four games for Havana as a 13-year-old. Armenteros has not been declared a free agent.
Alfredo Rodriguez, 21, INF
The 2014-15 Serie Nacional Rookie of the Year, Rodriguez is a glove-first player with good speed (6.6 seconds in the 60-yard dash). He's a high-energy player who is making progress at the plate. Rodriguez has not been declared a free agent.
Julio Alfredo Martinez Wong, 24, LHP
Wong is a polished strike-thrower with a fastball that ranges from 87-90 mph. He might not be the most electric pitcher on the market, but he knows what he's doing on the mound and has an assortment of pitches, including an advanced curveball. Wong has not been declared a free agent.
Jonatan Machado, 16, INF/OF
The speedy Machado has added mass to his 5-foot-10, 155-pound frame during the past few months. He profiles as a leadoff hitter and has been clocked at 6.5 seconds in the 60-yard dash. He can play shortstop and center field. Nicknamed "Ichiro," Machado is free to sign.
Carlos Sierra, 21, RHP
Sierra does not light up a radar gun, but he has emerged as an interesting option for teams looking for help at the back end of the rotation or in the bullpen. Sierra's fastball hovers between 89-90 mph, which is quite an improvement over the 86-89-mph range he threw in a showcase on Oct. 13 in front of 25 scouts. He throws a slider, a changeup and a curveball. The 6-foot-3, 200-pound Sierra played three seasons for Sancti Spíritus in Cuba's Serie Nacional and for the island's 16-and-under and 18-and-under national teams. He later pitched in the Canary Islands for the Tenerife Marlins in the Division de Honor de Beisbol, the top baseball league in Spain.
Sierra is free to sign.
More Cuban players subject to the international signing guidelines to watch: Infielders Randy Arozarena, Omar Estevez, Adriel Labrada, Lasaro Alonso, Alejandro Ortiz, Edwin Vassel, Yorkist Luis Rodriguez, Mario Miranda and Damian Leyba; outfielders Yordan Alvarez, Yordanis Linares, Henry Quintero, Anibal Sierra and Numberto Castellano; right-handed pitchers Juan Oviedo, Ronald Bolanos, Ramon Ernesto Perez, Yunieki Garcia, Julio Montesino and Rodry Castello; catcher Alberto Diaz Martinez; outfielder Osmer Aguila; right-handed pitched Victor Baro; left-handed pitcher Noel Ortiz; shortstop Luis Periche; catcher Freddy Portilla; right-handed pitcher Carlos Gonzalez.
Jesse Sanchez is a national reporter for MLB.com. Follow him on Twitter @JesseSanchezMLB.