"It is a little bit sad, but it's also business," Mostert told Bay Area reporters on a video call Wednesday. "I told Matt that I was angry. But at the same time, I was happy just because he's getting an opportunity to go down to Miami and to try to be one of the best backs in Miami that he can possibly be.
"And I know he's going to take that step because that's all Matt does."
Because of their depth at running back, the 49ers opted to deal Breida to the Dolphins for a fifth-round draft pick. The 49ers selected West Virginia offensive lineman Colton McKivitz with the pick general manager John Lynch acquired in exchange for Breida.
Breida has a chance to flourish with his new team. He joins an unimpressive Dolphins backfield that includes running backs Kalen Ballage, Myles Gaskin, Jordan Howard and Patrick Laird. Miami's leading rusher last season was 37-year-old quarterback Ryan Fitzpatrick with 243 yards.
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Breida, who earned his job with the 49ers after arriving in 2017 as an undrafted rookie from Georgia Southern, was a top performer for the team during his three seasons despite battling a variety of injuries. In 2018, he led the 49ers with 814 yards rushing while averaging 5.3 yards per carry.
He was the 49ers' leading rusher for most of last season until he missed time late in the season with an ankle injury. Breida was second on the team behind Mostert with 623 yards rushing with a 5.1 average in 13 games. But he fell out of the team's rotation in the playoffs.
"Being undrafted and fighting his way up the roster, he had the same qualities I had when I was doing the same thing when I was undrafted," Mostert said. "That's where we share our bond.
"He said, ‘Hey, Raheem, we're still going to be contacting each other week-in and week-out.' And I said, ‘You damn right we are.' He's my brother and I'm always going to look after my little brother, no matter what. Our bond is unbreakable. It's something that's going to last for a lifetime. I'm so excited for him."
The 49ers figure they should be in good shape at running back even without Breida. The club hopes Jerick McKinnon remains healthy and gives the 49ers a pass-catching threat out of the backfield on third downs. McKinnon joins Mostert, Tevin Coleman and Jeff Wilson. The 49ers also added undrafted rookies Salvon Ahmed (Washington) and JaMycal Hasty (Baylor).
"We're still going to be a close-knit group, and it helps because we still have the rookies to crack on, too," Mostert said. "It's pretty cool because they're also chiming in and getting used to how we operate within the room."
Raheem Mostert sad, excited by 49ers trading Matt Breida to Dolphins originally appeared on NBC Sports Bay Area