Nimmo reportedly agreed to an eight-year, $162 million contract, and Robertson, most recently with the Philadelphia Phillies, reportedly will get a one-year, $10 million deal.
The Mets previously added starting pitchers Justin Verlander and Jose Quintana and re-signed closer Edwin Diaz this winter. On the down side, they lost free agent starter Jacob deGrom to the Texas Rangers.
Nimmo, 29, will receive a contract with the second-highest value in franchise history, trailing just the 10-year, $341 million pact that Francisco Lindor signed in April, according to ESPN.
Nimmo hit .274 with a .367 on-base percentage, a .433 slugging percentage, 16 homers and 64 RBIs in 151 games this year. He tied for the National League lead with seven triples.
In seven major league seasons, all with the Mets, Nimmo has a .269/.385/.441 batting line with 63 home runs and 213 RBIs in 608 games.
Robertson, 37, split last season between the Chicago Cubs and the Phillies, finishing a combined 4-3 with 20 saves and a 2.40 ERA in 58 relief appearances. He has pitched for the New York Yankees (2008-14 and 2017-18), Chicago White Sox (2015-17), Philadelphia (2019 and 2022), the Tampa Bay Rays (2021) and the Cubs (2022).
In 731 career appearances, all but one of them in relief, Robertson is 57-36 with 157 saves and a 2.89 ERA. He was a key member of the Yankees’ 2009 World Series championship team, and he made four scoreless appearances for the Phillies in the 2022 World Series that they lost to the Houston Astros.