In a meeting Saturday to relay the news, manager Terry Collins apologized to Gee in part for having him make unnecessary minor league rehab starts while on the disabled list for a mild groin injury.
Gee, 29, candidly said he feels the decision to move him to the bullpen diminishes his value to the team as well as his trade value. Still, he pledged to do his best in the unfamiliar role.
Gee is earning $5.3 million season. He has one more year of arbitration eligibility.
He is 0-3 with a 4.46 ERA in six starts this season. He allowed seven runs (four earned) in four innings in his return from the disabled list at San Diego on Wednesday, when the Mets officially launched a six-man rotation that lasted only days.
"I felt like any value -- if I had any at all -- before this, it's probably gone," Gee said. "What am I going to do out of the pen? I felt like there's really not a whole lot of good that comes from it.
"There's nothing I can do. Obviously, I'm going to do the best I can. My biggest concern is that if there was any glimmer of value before this, I don't see how there would be any more when I get moved to the pen -- the value trade-wise or value to the team. I'm definitely unproven in the pen. You don't know what you're going to get, but you know what you're going to get out of the guys that are already there."
The Mets had described the six-man rotation as a way to conserve the innings for Matt Harvey as he returns from Tommy John surgery, as well as for young starters Jacob deGrom and Noah Syndergaard to avoid innings caps and the need to be shut down in September.
However, the Mets quickly reversed course on the six-man-rotation plan, deciding it was unwise to continually give their top pitchers two extra days of rest between starts, given the number of team off days on the schedule in the coming weeks.
Collins said the Mets will confront the innings-limit issues for Harvey, deGrom and Syndergaard when they cross that bridge late in the season. The manager added, though, that he believed shutdowns could be avoided through September call-ups being used as spot starters and by other means.
With Gee's move to the bullpen, the Mets now have eight relievers and four bench players. Collins said he expects that to be rebalanced within the week as catcher Travis d'Arnaud and second baseman Dilson Herrera return from the DL.
Gee has been treated inconsistently all season, which Collins also apologized for in their meeting.
Although Gee was the team's Opening Day starter in 2014, he arrived at spring training this year penciled in for a bullpen role.
Gee ultimately broke camp with the team in the rotation. However, when he landed on the disabled list last month with a mild groin injury, the Mets filled his rotation spot by promoting top prospect Syndergaard. Syndergaard has performed well, so the Mets decided to go with the six-man rotation once Gee was activated -- that is, until they abandoned the plan days later.
Asked if he was upset, Gee described his current state more as numbness.
"I'm almost at the point now where I just don't even care anymore," he said. "I'm kind of over it all. I'll do the best I can out of the pen right now."