PORT ST. LUCIE Fla. -- Left-hander Sean Manaea will begin the season in the New York Mets' bullpen, manager Carlos Mendoza announced Saturday morning. Mendoza said Manaea will be used in a piggyback role, meaning he will relieve a starter to log multiple innings in a game, but declined to share which game he'll pitch. The Mets' Opening Day rotation, in order, will be Freddy Peralta, David Peterson, Nolan McLean, Clay Holmes and Kodai Senga. "Six guys throwing the ball really well," Mendoza said. "And we were pretty honest with all of them at the beginning of camp. If everyone was healthy, we were going to have to make some tough decisions and one of them was going to be pitching in that type of role." Mendoza said the team decided a rotation of five was best for two turns given its early schedule, which includes an off day after next Thursday's season opener against the Pittsburgh Pirates.…