Rackers was among the first round of cuts Monday as the Redskins trimmed their roster to 75 players.
Gano won a competition that was mainly decided on the practice field. The Redskins attempted only two field goals in their first three preseason games, both by Rackers. He made a 28-yarder and missed from 54.
The 25-year-old Gano missed an NFL-high 10 field goal attempts last season, but five were blocked. He's made 74 percent of his attempts since joining the Redskins during the 2009 season, the second-worst percentage in the NFL over that span.
The 36-year-old Rackers has played 12 seasons with Cincinnati, Arizona and Houston. He made 32 of 38 field goal attempts -- including 4 of 5 from 50-plus yards -- last year with the Texans.
The Redskins also announced right tackle Jammal Brown is recovering from another hip surgery, ruling him out for the first six games of the regular season.
Coach Mike Shanahan said Monday that Brown will need four to six weeks to recover from the surgery, which Brown had late last week. The Redskins moved the lineman from the active physically unable to perform list to the reserve physically unable to perform list, which means he can't play in the first six weeks of the NFL season.
Brown was a first-round draft pick by the New Orleans Saints in 2005 and went to the Pro Bowl in 2006 and 2008, but he missed the 2009 season after surgery on his left hip. The Saints then traded him to Washington, where he has struggled to remain healthy.
Brown was limited by his ailing hip in 2010 and missed the last four games of last season when it flared up again. He then re-injured his hip while running sprints on the eve of this year's training camp. The latest surgery is again on his left hip, but his right hip has also been sore.
"He's saying right now that the surgery really helped him. He's feeling good," Shanahan said. "Realistically, from my perspective, you never know. You're always hoping that a guy's going to come back, but it's been bothering him for a while."
Brown's injury makes Tyler Polumbus the probable starting right tackle for the regular season opener against the Saints on Sept. 9. The six-year veteran started three games last season and has held the spot throughout training camp and the preseason.
"He's done a very good job," Shanahan said.
The offensive line remains the major question mark for the Redskins, who have allowed 40-plus sacks in each of the last three years. Left guard Kory Lichtensteiger has missed the entire preseason while recovering from left knee surgery, but he has returned to practice and said he remains on pace for the opener.
"I'm encouraged," Lichtensteiger said. "I don't see anything standing in the way of me being ready."
Information from The Associated Press was used in this report.