Mets manager Terry Collins confirmed that Montero would be called up from Triple-A Las Vegas to start Friday's game against the Marlins, Anthony DiComo of MLB.com reports.
The Mets are expected to make the transaction official in the hours leading up to Friday's series opener. Montero will get the first crack at entering the rotation in place of Noah Syndergaard (back), who could miss nearly three months, pending the results of the second opinion he was scheduled to receive Wednesday. Collins hasn't committed to starting Montero beyond Friday, however, so it will be up to the 26-year-old to prove that he's deserving of extended run in the rotation. Montero's track record at the big-league level probably won't warrant a speculative pickup outside of most NL-only leagues, as he owns a 5.51 (5.00 FIP) and 5.8 BB/9 rate over 80 career innings.