Butto will be added to the Mets' major-league roster Friday, Tim Healey of Newsday reports.
Butto is expected to work out of the bullpen down the stretch. The 25-year-old has posted a 4.30 ERA in 14.2 innings (two starts, two relief appearances) this season at the major-league level and a 5.93 ERA in 91 innings (19 starts) with Triple-A Syracuse.