Alexander played all 16 games of his rookie season when safety Daniel Bullocks suffered a season-ending knee injury during a preseason game against the Indianapolis Colts. During that 2007 season Gerald recorded 81 tackles, 59 solo and 22 assisted. He also had 2 sacks, interceptions and fumble recoveries.
On June 26, 2009, he was traded to the Jacksonville Jaguars for Dennis Northcutt. On October 19, 2010, the Jaguars released Alexander.
On November 23, the Panthers signed Alexander. He became a free agent after the season.
Alexander signed with the Miami Dolphins on August 28, 2011. Alexander was released on September 2, 2011 by the Miami Dolphins. Re-signed on October 19, 2011.
New York Jets
Alexander was signed by the New York Jets on December 13, 2011 to add depth to the safety position following a season-ending injury to starting safety Jim Leonhard.