Mattison is in line to sign with the Raiders, Tom Pelissero of NFL Network reports.
The Vikings officially released Mattison on Monday.
The Vikings informed Mattison they will be releasing him Thursday, Adam Schefter of ESPN reports.
Mattison rushed seven times for 24 yards and caught his lone target for five yards in Sunday's 30-20 loss to the Lions.
Mattison (ankle) doesn't have an injury designation for Sunday night's game against Green Bay.
Mattison (ankle) practiced on a limited basis Thursday.
Mattison (ankle) was listed as limited on Wednesday's estimated practice report.
Mattison had two carries for minus-1 yard during Sunday's 30-24 defeat to the Lions.
Mattison (ankle) is active for Sunday's game against the Lions.
Mattison (ankle), who is listed as questionable for Sunday's game against the Lions, is expected to play, but he may be less than 100 percent healthy, Tom Pelissero of NFL Network reports.