The Red Sox added two pitchers to their 40-man roster ahead of Tuesday’s 6 p.m. deadline, protecting the prospects from being exposed in the Rule 5 Draft.

Right-handed pitchers Wikelman Gonzalez and Luis Perales were added to the roster. Both additions were widely expected, given that they represent Boston’s top two starting pitching prospects and would have almost certainly been poached by another club if left unprotected.

The big surprise was who was left exposed.

Left-hander Shane Drohan, considered a top candidate to be added to the 40-man, was surprisingly left unprotected. Not long ago Drohan looked to be Boston’s most MLB-ready starting pitching prospect, but his performance notably tailed off as the season went on.

Gonzalez was recently named Red Sox Minor League Starting Pitcher of the Year after posting a 3.96 ERA with 168 strikeouts over 111.1 innings between High-A Greenville and Double-A Portland. The 21-year-old from Venezuela got off to a rocky start thanks to some serious command issues, but finished strong and posted a 2.42 ERA following his midseason promotion to Portland. He currently ranks as Boston’s No. 9 prospect according to MLB Pipeline.

Perales, Boston’s No. 10 prospect, also enjoyed a breakout season in which he posted a 3.91 ERA with 115 strikeouts over 89.2 innings. The fellow Venezuelan was Rule 5 eligible despite being only being 20 years old, and he’s still a long way from the majors after only just reaching High-A this past year.

Drohan, ranked No. 18, might have been the next in line to contribute at the big league level next season. The 24-year-old got off to an unbelievable start in Portland this spring, getting promoted to Triple-A barely a month into the season after going 5-0 with a 1.32 ERA over his first six starts. Things didn’t go as smoothly once he got to Worcester, however, and he finished the season with a 5.05 ERA over 123 innings.

Evidently the club was troubled by his performance, and now it would be a shock if he isn’t picked by another club in next month’s Rule 5 Draft.

Other potential candidates left exposed included pitchers Ryan Fernandez, Grant Gambrell, Justin Hagenman, Angel Bastardo and Zach Penrod along with infielders Eddinson Paulino and Brainer Bonaci, who likely would have been protected before he was placed on the restricted list for violating MLB’s joint domestic violence, sexual assault, and child abuse policy.

Right-hander Noah Song, who was taken by Philadelphia in last year’s Rule 5 Draft despite missing three years due to his U.S. Navy obligations, and who was later returned to the Red Sox after failing to stick with Philadelphia’s big league roster, was also left unprotected.

Players are eligible for the Rule 5 Draft after five years if they signed with their clubs at age 18 or younger, or after four years if they signed at age 19 or older.

The Red Sox 40-man roster is now at 39.