Nelson will get a two-year, $15 million deal, a source tells Schefter, including $13 million guaranteed.
"Absolutely excited to be a part of the offense," Nelson told reporters during a conference call. "I think [coach Jon Gruden] is a guy who has a creative mind. I think he's going to stay true to who he is, but also is willing to learn and adjust to what he has and play to the skill level that each of his players have. I think everyone knows the intensity that he's going to bring, he'll bring it day in and day out."
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, respectively.
Nelson spent 10 seasons in Green Bay. He and quarterback Aaron Rodgershold the Packers record for most touchdowns by a quarterback-receiver duo with 65.
Last season, he saw his production drop after Rodgers broke his collarbone. To that point, he had six touchdowns in the first five games of the season, but he didn't catch another one. He was released Wednesday.
Nelson finished the season 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 yards and 14 touchdowns. He had missed the 2015 season because of a torn ACL.
Oakland's signing of Martin, also known as the "Muscle Hamster" due to his 5-foot-9, 223-pound frame, is intriguing. Martin has been a lead back his entire six-year NFL career, and Gruden has said he looks forward to coaching Marshawn Lynch, who is due a $1 million roster bonus on Sunday. Lynch posted 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 could be the Raiders' new lead back.
Martin, who was born in Oakland and grew up in Stockton, California, told reporters Thursday, "This is my homecoming."
He said that he met Lynch after his rookie year at the Pro Bowl and "can't wait to pick his brain and watch him and see how he plays the game and practices and all that."
Martin said he will accept whatever role the Raiders need him to play and called Lynch "a great back."
"He's definitely made his mark in the league. Whatever role they want me to play, I'm willing to play. I'm not sure how many carries I'll be getting, how much carries we'll be splitting," he said.
Martin, 29, 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 he signed before that season. That facilitated his release.
Crabtree seemed destined to be done in Oakland. He had become a forgotten man the last two weeks of the season, with a combined five targets after getting 30 total targets in Weeks 14 and 15.
He joined the team in 2015, and ranks in the top five in receiving touchdowns over the past three seasons. He had three straight seasons with at least eight touchdown receptions in Oakland, and led the team in receptions and touchdowns last season.
But his production was down --he collected only 618 yards in 2017. He also served a one-game suspension following a scuffle with cornerback Aqib Talib, then with the Denver Broncos, and his career in Oakland ended with talk of locker-room dissension.
Crabtree had 579 catches for 6,870 yards (11.9 yards per catch) and 51 TDs in 125 games over nine seasons. But he is third in the league in drops since 2015, with 19 over that time. One of the drops was at the goal line at Philadelphia on Christmas night, with his new coach in ESPN's Monday Night Football booth.
ESPN's Jenna Laine and Rob Demovsky contributed to this report.
Raiders wanted Nelson so badly 'they wouldn't let him out of building'
Adam Schefter reports that Michael Crabtree was released by the Raiders after the team was able to sign former Packer Jordy Nelson.
Schefter: Raiders still trying to reel in Jordy Nelson
Adam Schefter reports that Jordy Nelson hasn't left Oakland after meeting with the Raiders as they are trying to finalize a deal.