Next, veteran right-hander Jose Contreras was given his unconditional release. That created a vacancy on the 40-man roster for Morton, who accordingly went from the 60-man disabled list to the PNC Park mound to face the San Francisco Giants.
Left-hander Jeff Locke, originally scheduled to face Los Angeles on Saturday, will instead move into the Friday slot originally occupied by Burnett. Locke last pitched Sunday in Chicago; thus, with Monday having been an off-day, he will be going on the regular four days' rest.
Rookie Gerrit Cole remains on tap for Sunday's start. Saturday's starter has not yet been determined.
"Charlie will be activated," Pirates manager Clint Hurdle Hurdle had said a few hours before the first pitch Morton would make to punctuate his return from Tommy John surgery. "He will pitch. He's a lock. We just haven't decided on the corresponding move. We're still working through this, and we'll take all the available time, right up to pregame."
The decision to put Burnett on the disabled list means he will miss two starts. His status is retroactive to Sunday, making him eligible to return June 23.
Burnett pitched into the ninth inning for the first time this season in his most recent start, Saturday against the Cubs. He allowed four hits and two runs in 8 1/3 innings to earn his first victory since May 3.
Contreras, 41, had been on the DL since May 28 with lower-back inflammation and had been set to begin a Triple-A rehab assignment Thursday night before the decision to release him. Contreras, who underwent his own Tommy John surgery last June, made seven appearances for the Pirates, allowing seven hits and walking six in five innings.
Tom Singer is a reporter for MLB.com and writes an MLBlog Change for a Nickel. He can also be found on Twitter @Tom_Singer. This story was not subject to the approval of Major League Baseball or its clubs.