Raiders add WR Jordy Nelson and RB Doug Martin, cut WR Michael Crabtree

?ALAMEDA, Calif. - The Oakland Raiders have given their offense a new look, adding wide receiver Jordy Nelson and running back Doug Martin while releasing receiver Michael Crabtree, sources tell ESPN's Adam Schefter.

Nelson will get a two-year, $15 million deal, a source tells Schefter, including $13 million guaranteed.

Terms of the Martin deal are not yet known though the Raiders will save more than $7.68 million against the salary cap with the release of Crabtree, who was due base salaries of $7 million and $7.5 million in 2018 and 2019.

Nelson saw his production drop last season after quarterback Aaron Rodgers broke his collarbone. To that point, he had six touchdowns in the first five games of the season, but he never caught another one.

He finished with 53 catches for 482 yards and six touchdowns.

Just one season before, he was the NFL's comeback player of the year when he caught 97 passes for 1,257 and 14 touchdowns. He had missed the 2015 season because of a torn ACL.

Oakland bringing in Martin, also known as the "Muscle Hamster" due to his 5-feet-9, 223-pound frame, is intriguing. Martin has been a lead back his entire six-year NFL career and returning Raiders coach Jon Gruden has said he looks forward to coaching Marshawn Lynch, who is due a $1 million roster bonus on Sunday. Lynch had a cryptic Tweet on Wednesday.

Still, Gruden could be trying to replicate the Thunder and Lightning backfield from his first tenure as Raiders coach with Lynch and Martin playing the roles of Tyrone Wheatley and Napoleon Kaufman. Or Martin is the Raiders' new lead back.

Martin, a two-time Pro Bowler, was released by the Tampa Bay Buccaneers on Feb. 20 after averaging just 2.19 yards per rushing attempt over the past two seasons.

Martin, who was due to make nearly $7 million in 2018, started the season with three games remaining on a four-game suspension for violating the league's policy on performance enhancing substances in 2016. He then was benched in favor of second-year back Peyton Barber for the final three games of the 2017 season and was a healthy scratch in Week 15 for violating a team rule.

He entered a drug rehabilitation program and was suspended for the final game of the 2016 season. Because Martin engaged in conduct detrimental to the team, the Bucs were no longer on the hook for any of the guaranteed money from the five-year, $35.75 million deal signed before that season. That facilitated his release.

"You cheered when I scored touchdowns and supported me when I stumbled," Martin said in a Facebook post directed to the Bucs and their fans after being released. "You embraced me not only as a player, but also as a person. That is special. Thank you."

Martin, 29, rushed for 1,402 yards in 2015, second only to Adrian Peterson that season and second most in his career. He rushed for 4,633 rushing yards with the Bucs, which was fourth in team in history behind James Wilder, Mike Alstott and Warrick Dunn. Martin's 11 100-yard rushing games are tied for second in Bucs franchise history.

ESPN's Jenna Laine and Rob Demovsky contributed to this report.