New San Francisco 49ers cornerback Richard Sherman says facing his former side the Seattle Seahawks twice a year was one of his main motivations for joining his old team's NFC West rivals.

The 49ers' general manager, John Lynch, felt his side could offer the 29-year-old something unique with the chance to face the Hawks, who released him last week ahead of free agency. 

And Sherman agreed that opportunity had played a part in his choice, as he reflected on the negative reaction of some fans of his former team. 

"I'm vengeful in that way," Sherman said to The MMQB after signing with a divisional rival.

"I love the [Seahawks] fan base to death, and I loved playing there. It was such a great opportunity. I helped the organisation get to a great place and stay there. But now it's like I abandoned them. 

"People are out there burning my jersey. Come on. I'm not the one who let me go. They let me go. I didn't abandon anybody."

Sherman, who acted as his own agent, revealed to ESPN that his new three-year deal with the 49ers is filled with incentives and worth up to $39.15million. He then told The MMQB it includes guarantees that roll over each season if he makes the Pro Bowl.

"I don't think any agent in the business could have done a better job of negotiating this contract," Sherman said. 

"It gives me the ability to control my destiny. The 49ers have skin in the game. I have skin in the game. In my former contract, no matter what I did this year, nothing would be guaranteed to me next year. I couldn't feel secure in my contract. Now, if I play the way I know I'm capable of playing, I know I'm going to get paid."

Paraag Marathe, executive vice president of football operations for the 49ers, felt Sherman was prepared to secure the best possible offer.

"Richard came into the meeting with us having read all the contracts for all the top cornerbacks past and present," Marathe said. 

"[Sherman] studied our contracts and knew who we'd given real guaranteed money to."

Once the offer was on the table, Sherman called the Seahawks, who had released him just a day before, to ask if they could match the offer. They refused and will now have to look at Sherman on the opposite sideline at least twice in 2018.