The Raiders waived linebacker Horace Miller on Wednesday to make room on the roster.
Alexander is entering his ninth NFL season. He has played for Washington and Arizona and spent time on the practice squads for Carolina and Baltimore in his career.
Alexander has played 111 games with 154 tackles, nine sacks, three forced fumbles, three fumble recoveries and six passes defensed. He also has 94 special teams tackles in his career.
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