Montero, 25, took the news in stride as he prepared to return to Tacoma, where he was leading the Pacific Coast League in hitting at .332 with 15 home runs and 68 RBIs prior to joining the Mariners.
"I'm fine. I'm happy," Montero said. "I just have to keep working hard and thinking about my daughter. I'm going to see her tonight, so I'm happy. I'm not making the decisions. I don't control that. I'm happy where I am right now."
Montero has made big strides this season, losing about 40 pounds over the offseason and refining his game at first base in Tacoma. But the Mariners don't have an obvious opening on their 25-man roster after acquiring veteran Mark Trumbo to fill a similar right-handed role at DH and backup at first base behind left-hander Logan Morrison.
So Montero will continue doing what he can in Tacoma and await his next callup.
"They gave me an opportunity to be here and it was fun," he said. "I want to keep working hard to be up here, I don't know when. Maybe tomorrow again, I don't know. But I'm going to continue to do my best to be out here to help this team to win."
Montero showed a patient approach in his brief time, taking three walks -- including one in his first at-bat Sunday against CC Sabathia -- at a time many youngsters would be swinging at everything trying to prove they belonged in the short window provided.
"That was important," Montero said. "Right here is a little different. You have to see more pitches and you're going to give more competition. That's what I did. I was patient, waiting for my pitch and good things happened."
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.