In what can be considered one of the biggest trades after the draft thus far, the San Francisco 49'ers traded cornerback Willie Middlebrooks to the Denver Broncos for cornerback John Engelberger.

Middlebrooks was the Broncos' first-round pick in 2001, but was never able to earn a starting job with the team. He'll likely be behind cornerbacks Ahmed Plummer and Shawntae Spencer on the 49'ers.

Engelberger has played well for the 49'ers since being their second-round draft pick in 2000. Last year, he led the team with six sacks. Engelberger became expendable after the team decided they would switch to a 3-4 defense this season. Marques Douglas was already signed back in April to fill Engelberger's shoes.

"We're in need of some depth in the secondary, and we do have a couple of extras where Engelberger was playing," Nolan said.