Matsuzaka agreed with the Red Sox on a six-year, $52-million contract Thursday, ending a month of contentious negotiations between the Japanese pitcher, his agent Scott Boras and the Red Sox.

''It was mentally draining,'' Matsuzaka said. ''It was tough. I'm not used to having an agent, and leaving everything up to him was something that was new to me.''

Most players in Japan don't have agents and contract negotiations are usually held just between the team and the player.

The 26-year-old right-hander will join Curt Schilling in a rotation that includes Josh Beckett, Jonathan Papelbon and Tim Wakefield. The Red Sox also will have another Japanese pitcher, lefty reliever Hideki Okajima, in training camp.

Matsuzaka said he knows the expectations will be high but he is looking forward to playing for the Red Sox.

The Red Sox bid $51.11 million for the right to negotiate with Matsuzaka, but they had just 30 days -- until midnight Thursday -- to sign him to a contract.

At times, it looked like Matsuzaka might be returning to Japan to play for his former team the Seibu Lions.

Matsuzaka flew to Southern California for talks with Boras and the Red Sox last week before flying on to Boston on Wednesday to complete the deal.

''There were times when I thought I'd be heading back to Japan without a deal,'' Matsuzaka said. ''Fortunately, everything worked out in the end.''

-- ASSOCIATED PRESS