The tight end told ESPN: "It was tough for me because I really care about Alex. I love the guy. It's hard to see him leave, but I know the business. I understand it. It's the nature of the business.
"It's been an emotional rollercoaster for Alex. He's been up, he's been down, but he still can hang in there. He's a classy guy. You saw what happened to him this year. He remained a 49er and he didn't complain.
"I take my hat off to Alex for just the growth as a man. We were hungry, we wanted to win. We've been through so much with numerous coaches coming in and out, but we still wanted to win no matter what."
Smith was replaced in the starting lineup by Colin Kaepernick during the 2012 NFL season.