Tohoku Rakuten Eagles right-hander Kazuo Fukumori and Chiba Lotte Marines right-hander Yasuhiko Yabuta were among the 68 eligible players who filed for free agency Wednesday.
Fukumori, who is aiming to apply his trade in the major leagues, completed the necessary procedure to declare himself a free agent while Yabuta said he plans to go the same route. Both players' moves are drawing close attention.
"I want to hear what other teams have to say about me, so I had planned to do this all along," said Yabuta, who went 4-6 with four saves with a 2.73 ERA in 58 games in 2007.
Hiroshima Carp infielder Takahiro Arai, meanwhile, is expected to declare himself a free agent with the purpose of moving to another Japanese club, baseball sources said. He is scheduled to hold a press conference on Thursday.
Arai met the club for talks three times but had been undecided on whether to exercise his right to free agency.
He joined Hiroshima in 1999 after he was selected in the sixth round of the draft.
Lotte Marines closer Masahide Kobayashi and Hiroshima right-hander Hiroki Kuroda both have already said they will test the free agent market.
Meanwhile, Chunichi Dragons outfielder Kosuke Fukudome, Chunichi right-hander Masafumi Hirai and Seibu Lions outfielder Kazuhiro Wada are also considering leaving their respective clubs but have not filed for free agency.
Yomiuri Giants outfielder Yoshinobu Takahashi has said he will not exercise his right to be free agent and plans to return to the Central League club next year.
Players eligible for free agency have until Monday's deadline next week to complete the procedure and their names will be announced by the Japanese baseball commissioner's office the following day.
Clubs, including those in the major leagues, will be allowed to negotiate with free agents from next Wednesday.