For example, here's what happened when the Mets wanted to option Kodai Senga last season:
Senga, 32, is in the third year of a five-year, $75 million contract. Prior to joining the Mets, he pitched 11 seasons for the Fukuoka Softbank Hawks in Japan. As part of the contract, Senga can only be sent to the minors with his consent, so he had to sign off on this trip to Triple-A. That is a clause commonly given to veteran players who come over from foreign leagues.