CHICAGO -- Top pitching prospect Duane Underwood was one of four players the Cubs added to the 40-man roster Friday, joining pitcher Jack Leathersich, catcher Victor Caratini and outfielder Jacob Hannemann.
With the addition of the four, plus left-hander David Rollins, who was claimed from the Mariners earlier Friday, the Cubs' 40-man roster stood at 39.
Teams had until 7 p.m. CT on Friday to determine which players they wanted to add to their 40-man rosters. Those left unprotected will be exposed to selection in the Rule 5 Draft, which will take place Dec. 8, the last day of the Winter Meetings. Those eligible to be selected include any player not on the 40-man roster who signed in 2012 at 18 years or younger, or in 2013 at 19 years or older.
A team that makes a selection during the Major League phase of the Draft must pay $50,000 and commit to carrying the selected player on its active roster through the entirety of the following season. A selected player can be offered back to the original club for $25,000. The Cubs did not lose a player in the Major League phase of the Rule 5 Draft last year.
Underwood was ranked sixth on MLB.com's list of Top 30 Cubs prospects; Caratini was 15th and Hannemann 19th.
A second-round pick in 2012, Underwood, 22, was 6-3 with a 2.58 ERA in 14 starts at Class A Advanced Myrtle Beach in 2015 and earned midseason Carolina League All-Star honors. Injuries limited him this year, and he pitched at four levels, making 18 starts. In 73 innings, Underwood struck out 62 and walked 35. He finished at Double-A Tennessee, where he was 0-5 with a 4.91 ERA in 13 games. He also made a pair of starts for the Mesa Solar Sox in the Arizona Fall League.
Caratini, 23, batted .291 at Tennessee this season, hitting six home runs and driving in 47. A midseason and postseason Southern League All-Star, he played for the Mesa Solar Sox in the AFL this year and batted .226 in 19 games. A switch-hitter, he was acquired from the Braves in the July 2014 trade for James Russell and Emilio Bonifácio.

Hannemann, 25, a third-round pick out of Brigham Young in the 2013 Draft, batted .247 in 74 games at Tennessee, his first full season at the Double-A level. He posted a .326 on-base percentage, 79 points higher than his batting average, and a .426 slugging percentage, good for a .752 OPS.

Leathersich, 26, came up through the Mets organization and appeared in 17 games in relief with the big league team in 2015 but was then sidelined with elbow problems and underwent Tommy John surgery in July that year. He signed with the Cubs as a free agent in December 2015 and appeared in 26 games (one start) in the Minor Leagues this year. In five games at Triple-A Iowa, the lefty walked six and struck out six over five innings.