The 6-foot-4, 200-pounder was 4-3 with a 3.74 ERA in nine starts for Triple-A Tacoma. He'll square off against Yankees lefty CC Sabathia, a veteran of 433 starts over 15 Major League seasons.
The Mariners won't officially announce a roster move for Montgomery until Tuesday, when they'll need to send down a reliever to open up a spot for him, but there's no mystery to the move after Montgomery, the Mariners' No. 24-ranked prospect, was scratched from his scheduled start with Tacoma on Sunday.
"He's done well down there," manager Lloyd McClendon said. "His stuff plays at this level. It's just a matter of whether he can execute. We'll find out tomorrow."
Montgomery was one of baseball's top pitching prospects in his initial years in the Minors, rated the No. 31 overall prospect in baseball in 2012 by MLB.com. He was traded to the Rays as part of the James Shields-Wil Myers deal in December 2012 and was 10-5 with a 4.29 ERA in 25 starts for Tampa Bay's Triple-A Durham club last year.
• Injured Mariners right-hander Hisashi Iwakuma played catch at 120 feet prior to Monday's game with the Yankees and seems to be progressing better now after five weeks on the disabled list with a strained right lat muscle.
McClendon said Iwakuma will throw his first bullpen session since the injury on Thursday, then will likely throw another bullpen session and simulated game on the team's next road trip as he works toward a Minor League rehab stint of likely two or three starts with Tacoma. If all goes well, Iwakuma might be ready to return shortly before the All-Star break.
"He's on his way," McClendon said. "He's progressing very well."
• Robinson Cano met the New York media prior to Monday's series opener and patiently answered questions about his slow start. Cano said he feels good at the plate and expects his results to improve as well as those of a team he believes will be contending down the stretch. As for his choice to leave New York?
"I would never regret my decision," he said. "I'm happy here. The way they've treated me is amazing. Not only the team, but the fans and city. I'm happy to be here."
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB, read his Mariners Musings blog, and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.