The Marlins avoided that with six players, including four pitchers.
Right-handers Michael Brady, Jose Urena and Angel Sanchez joined lefty Grant Dayton on the 40-man. The two position players added were catcher J.T. Realmuto and outfielder Brent Keys.
Miami's roster now is at 39, with 20 spots secured by pitchers.
Per league rules, players first signed at age 18 must be added to 40-man rosters within five years or they become eligible to be drafted by other organizations through the Rule 5 process.
Players signed at 19 years or older have to be protected within four years.
By not being added, Double-A Jacksonville infielders Danny Black and Mark Canha now are candidates for the Rule 5 Draft.
Clubs pay $50,000 to select a player in the Major League phase of the Rule 5 Draft. If that player doesn't stay on the 25-man roster for the full season, he must be offered back to his former team for $25,000.
According to MLB.com, Urena is the Marlins' sixth-rated prospect, while Realmuto is seventh, Sanchez is 10th and Keys is 17th.
Realmuto gives the Marlins four catchers on the roster, as he joins Jeff Mathis, Rob Brantly and Kyle Skipworth.
Keys is a speedy outfielder who falls into the mix of one of the deepest positions in the organization. At the Arizona Fall League, Keys enjoyed a solid season, batting .319 with one homer, two doubles, five RBIs, 11 runs scored and three stolen bases in 17 games.
Sanchez, acquired from the Dodgers in the Ricky Nolasco trade, made 10 starts for Class A Jupiter. He was 4-3 with a 3.22 ERA, plus 42 strikeouts in 50 1/3 innings.
Urena, 22, finished 10-7 with a 3.73 ERA for Jupiter in 27 games, with 26 starts.
Brady posted 23 saves for Jacksonville, and he fanned 55 in 53 innings. And in 30 relief appearances, Dayton had a 2.37 ERA, plus 56 strikeouts in 38 innings.