Before the 2007 season, "Baseball America" rated Humber as the fourth-best prospect in the Mets organization. That year, the Mets had nine pitchers competing for five spots in the starting rotation in spring training camp. Óliver Pérez, Tom Glavine, Orlando Hernández, and John Maine were the favorites for the spots in the rotation. Veterans Aaron Sele, Chan Ho Park and Jorge Sosa were also invited to camp so that the team could be patient with former first round draft choices Humber and Mike Pelfrey, who were considered the most promising pitchers in camp. Rated the 73rd-best prospect in baseball by "Baseball America" prior to the 2007 season, Humber competed for a spot on the Mets roster in spring training. However, Humber was optioned to the minor leagues during spring training in 2007. Assigned to the New Orleans Zephyrs of the Class-AAA Pacific Coast League (PCL), Humber had an 11–9 win–loss record and 4.27 ERA in 139 innings pitched. He allowed 129 hits and walked 44 while striking out 120 batters in 25 starts. For the season, Humber finished tied for fourth in the PCL in wins and had the tenth-best ERA. He had started the season by earning the PCL Pitcher of the week for the week ending April 22. That week he allowed 2 earned runs in 13 innings of work over two starts, earning a win on April 16 against the Nashville Sounds with six innings of work and suffering a blown save after seven innings against the Albuquerque Isotopes on April 21. He flirted with a no-hitter with the Zephyrs on August 22 when he entered the ninth inning without giving up a hit to the Iowa Cubs. In his subsequent start, he allowed only an unearned run on two hits over five innings, but he was removed from the game when a batted ball hit him in the shoulder.