Abreu signed with the Seibu Lions of Nippon Professional Baseball on Wednesday, Robert Murray of FanSided.com reports.
The Yankees placed Abreu on the 15-day injured list Friday with a right hamstring strain.
Abreu (2-1) earned the win Sunday against the Reds, striking out one over 1.1 perfect innings.
Abreu picked up a hold Friday against the Reds, allowing one walk and striking out one batter in a scorless inning.
Abreu pitched one inning against Texas on Sunday, allowing six runs on two hits and four walks while striking out one batter.
Manager Aaron Boone confirmed Sunday that Abreu will be included in the Yankees' Opening Day bullpen, Pete Caldera of The Bergen Record reports.
Abreu (elbow) was activated off the 15-day injured list Tuesday,
Abreu (elbow) had his rehab assignment transferred to Triple-A Scranton/Wilkes-Barre on Wednesday.
Abreu (elbow) started a rehab assignment with Double-A Somerset on Sunday.
The Yankees placed Abreu on the 15-day injured list Sunday with right elbow inflammation.