Defeater made a big announcement via social media tonight.
Per the band's Facebook page:
"Over the weekend it was decided to move forward as a band without the participation of Jay Maas due to personal & creative differences. All scheduled Defeater shows and tours will go on as planned and we wish Jay luck in his future endeavors. Thank you"
Their Wikipedia page has already been updated.
The band recently wrapped up their U.S. fall tour that ended with a sold out Middle East Downstairs show and will embark on a European tour next month. Maas owns and operates Getaway Recording in Haverhill, MA and has worked with local bands such as Rebuilder, Trophy Lungs and most recently, Somos.