Freeman was cut by Tampa Bay two weeks ago and was signed by the Vikings Oct. 7. He was elevated Wednesday to the starting position for Monday night's road game against the New York Giants.
"He has adapted to our system," Frazier said. "I like his work ethic. He has done enough for us to say that he is ready."
Freeman, 25, is the third starting quarterback for Minnesota this season. Christian Ponder started the first three games -- all loses -- before suffering a rib injury and Matt Cassel played the next two games during which the Vikings went 1-1.
Minnesota is 19th in the NFL in total offense and 21st in passing. The Vikings' 25.0 points per game average is tied for 17th in the league.
Freeman was a 2009 first-round draft pick by Tampa Bay out of Kansas State and started the first three games this season for the Buccaneers. He completed 45.7 percent of his passes for 571 yards and two touchdowns while being intercepted three times. He was replaced by rookie Mike Glennon.
Tampa Bay was 24-35 with Freeman at quarterback.