Following the secondary's worst performance of the season, the Miami Dolphins have made significant changes to the cornerback unit.
Richard Marshall, the team's top free agent addition and season-opening starter, was placed on injured reserve Wednesday because of the back injury that has sidelined him the past month.
According to the Sun-Sentinel, Marshall has a blood clot in his back, and he felt the injury could heal itself without surgery. But that hasn't been the case and he's opted to undergo a surgical procedure on Thursday.
"Stressful. That's the only word you can use to describe it," said Marshall, whom the Dolphins signed this offseason to a three-year, $16 million contract. "I can't practice, even if I wanted to. I can do certain things, but I can't do everything that I need to do to be out there."
Marshall, who won the starting spot opposite Sean Smith in training camp, has never missed an NFL game in his seven seasons before the back injury.
It is likely that Nolan Carroll will continue to start the rest of the season opposite Smith, and Jimmy Wilson will continue to serve as Miami's nickel cornerback.
However, the team signed Bryan McCann on Tuesday. The two-year veteran has played for the Cowboys, Ravens and Raiders.
McCann, a three-year starter at Southern Methodist University, played in 21 games since 2010, contributing 19 tackles, one interception and breaking up two passes.
And Miami claimed cornerback Brandon McDonald off waivers on Wednesday. McDonald, who was waived by Tampa Bay on Tuesday, is a 2007 fifth-round pick in 2007. He'll be playing for his fifth team since leaving the University of Memphis.
With McCann and McDonald, the Dolphins presently have six cornerbacks on the 53-man roster, and one (Julian Posey) on the practice squad. It's also possible that De'Andre Presley, the cornerback released on Tuesday to make room for McCann, could be re-signed to the practice squad.
The Dolphins hope to patch up a pass defense that has given up 298.2 passing yards per game, which is the third-worst average in the NFL.
The problem is, the Dolphins have allowed too many big plays (35 passes of 20 or more yards). Only three teams have given up more.