MIAMI -- Before delving too deeply into the free-agent and trade markets, the Marlins will first tend to some housekeeping. They are in the process of determining which Minor League players they want to prevent from being available in next month's Rule 5 Draft.
By Friday, teams must add to their rosters players they don't want to risk losing Dec. 8 in the Rule 5 Draft, which caps the annual Winter Meetings. Those eligible to be selected include any player not on the 40-man roster who signed in 2012 at 18 years old or younger, or in '13 at 19 years old or older.
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According to MLBPipeline.com, five of Miami's top 30 prospects are potential Rule 5 Draft candidates -- right-hander Luis Castillo (fifth), outfielder Austin Dean (sixth), infielder J.T. Riddle (11th), left-hander Raudel Lazo (28th) and right-hander Jose Adames (29th).
The Marlins have 32 players on their 40-man roster, with one being the late José Fernández. Technically, the organization didn't remove Fernandez from its roster after his death in a boating accident Sept. 25 off Miami Beach. But that formality could change by Friday, which means the club could fill as many as nine spots.
The Marlins have 69 players who could be eligible for the Rule 5 Draft, but only a dozen or so who are tough decisions regarding the 40-man roster.

Here's a look at some of the close calls to be protected by Friday:
The obvious
Castillo, Riddle and right-hander Drew Steckenrider
Castillo's stock rose all season. The 23-year-old started off at Class A Advanced Jupiter, before being promoted to Double-A Jacksonville. He combined for an 8-6 record with a 2.26 ERA in 131 2/3 total innings. His fastball velocity reaches 97 mph, and he projects to being a solid No. 3 big league starter.
Castillo likely will open 2017 at Triple-A New Orleans, but he could be called up to the big leagues as early as June.
Riddle is a left-handed-hitting infielder who may wind up at third base. The 25-year-old combined to hit .276/.326/.366 with four home runs and 53 RBIs in Double- and Triple-A in '16. Riddle also could go to the outfield and perhaps be a super utility player.

Steckenrider is a hard-throwing reliever who gained a lot of attention at the Arizona Fall League, striking out 15 in 13 innings. He likely will open at New Orleans, but he could be a factor in the bullpen during the season for the Marlins.
Worth watching
Dean, infielder Avery Romero, outfielder Dexter Kjerstad, infielder Austin Nola, Adames and Lazo
Dean, 23, was Miami's fourth-round Draft pick in 2012, and at Jacksonville, he hit 11 home runs and drove in 67. His slash line was .238/.307/.375.
Romero, 23, the Marlins' third-round choice in 2012, played second and third base in '16, starting off the year at Jupiter before advancing to Jacksonville, where he batted .190/.299/.290 in 36 games.
Kjerstad, 24, has shown power, belting 15 home runs at Jupiter, and he added two more in the Arizona Fall League. His slash line for the Hammerheads was .227/.291/.383. The question is whether the 24-year-old, a 50th-round Draft pick by the Reds in 2010, will show more signs of becoming a more complete hitter.

Nola is the brother of Phillies right-hander Aaron Nola. The 26-year-old infielder spent parts of the past two seasons at New Orleans and he's played in 566 Minor League games.
Adames, 23, throws 100 mph, but the question remains if he can throw enough strikes. The right-hander struck out 43 and walked 27 in 48 innings at Jupiter.
Lazo was injured coming out of Spring Training, and the lefty reliever showed promise in 30 1/3 innings at New Orleans, posting a 1.78 ERA. Without much lefty relief depth, he could be protected by Friday.