Takahashi, 34, agreed to a contract that will be worth $1 million if he makes the team, according to The New York Times, which first reported his signing. He can additionally earn up to $500,000 in performance bonuses.
Takahashi is the second Japanese pitcher the Mets have signed this offseason, and the third in two years. Late in 2009, the club signed right-handed reliever Ryota Igarashi to a two-year deal. And prior to last season, the Mets signed veteran lefty Ken Takahashi to a Minor League contract.
Ken Takahashi appeared in 28 games for the Mets in 2009, and signed with the Hiroshima Toyo Carp following the season.
Hisanori Takahashi, like Ken Takahashi, is capable of both starting games and pitching in relief. He was 10-6 with a 2.94 ERA for the Japanese Central League's Yomiuri Giants last season, and he is 79-66 over 10 seasons, all with the Giants. Takahashi features five pitches, including a screwball.
He will enter a fifth-starter competition that already includes right-hander Fernando Nieve and rookie left-hander Jon Niese. Manager Jerry Manuel indicated last month that Nieve is the favorite to win the job, while the club waits for Niese to fully heal from a hamstring surgery.
If Takahashi does not win a rotation spot, he could become a second left-handed option out of the bullpen along with Pedro Feliciano.
Igarashi, who signed a guaranteed two-year deal worth $3 million, is among the favorites to win a job setting up closer Francisco Rodriguez.
Jacobs, 29, hit .228 with 19 home runs for the Royals last season. Originally drafted by the Mets in 1999, Jacobs hit .300 with 11 home runs for New York in his rookie season of 2005, before heading to Florida in the deal that brought Carlos Delgado to Flushing. Jacobs will now be one of the players aiming to replace Delgado, who is unlikely to return to the Mets.
In 2008 with the Marlins, Jacobs hit .247 with a career-high 32 homers and 93 RBIs.
Riggans, 29, has caught 64 games over the past three seasons with the Rays, though he appeared in just seven games last year. Riggans will join a backup-catcher competition that also includes Henry Blanco, Chris Coste and rookie Josh Thole. Omir Santos is the presumed starter.
Anthony DiComo is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.