"The velocity wasn't there, the command wasn't there," Mets General Manager Sandy Alderson told New York media at the team's Florida spring training camp.
"We really didn't have to go too far beyond that to make a decision. We just got to the point where there was no reason to prolong it."
Perez, 29, will continue to be paid by the Mets this season but is free to sign with another team and hoped to do so.
"I think I've got more career," the left-hander told reporters.
Perez had been with the Mets since 2006 and signed a three-year, $36 million contract before the 2009 season.
Beset by knee problems that shortened his play in 2009 and 2010, Perez pitched poorly in spring training. He also gave up back-to-back home runs to minor league players in a weekend game against the Washington Nationals.
(Reporting by Gene Cherry in Salvo, North Carolina. Editing by Alan Baldwin)