2006-07: Brett Flemming had 51 points in 67 games for the Burlington Eagles in midget hockey and was selected in the second round (23rd overall) of the 2007 OHL Priority Draft by Mississauga St. Michael's Majors.
2007-08: Flemming appeared in 47 games as a rookie for St. Michael's. He scored 1 goal with 9 assists and was a team-best +15 with 30 PIM. Fleming scored his first career goal in a 4-1 win over Barrie on March 15. He was scoreless with 6 PIM in the Majors' four-game playoff series loss to Niagara. Flemming played 14 games for the Burlington Cougars in the OPJHL and had 1 assist with 12 PIM.
2008-09: Flemming played 64 games and scored 3 goals with 25 assists in his second season with the Majors. He was +21 (second to team leader Cameron Gaunce's +28) with 89 PIM as St. Michaels finished second in the Central division. In 10 playoff games, he scored 1 goal with 3 assists and was +2 with 2 PIM as the Majors defeated Barrie in the first round before falling to Brampton.
2009-10: Flemming scored a power play goal and had 23 assists as well as finishing +22 with 90 PIM in 68 games for St. Michael's. In the playoffs, Flemming had two assists in a Game 3 win over Peterborough in the first round. He finished with 5 assists and was +5 with 10 PIM in 16 playoff games as the Majors defeated Peterborough and Ottawa before falling to Barrie in the conference finals.
2010-11: Flemming was a team-leading +60 in his fourth OHL season with Mississauga St. Michael's. Flemming scored 4 goals with 39 assists and had 79 PMs as the Majors had the OHL's best record and advanced to the playoff finals, losing to Owen Sound in a seven-game series. In 20 playoff games he scored 1 goal with 12 assists and was +7 with 28 PMs. He was named to the OHL Third All-Star Team. Flemming signed a three-year, entry-level contract with Washington in December 2010.
2011-12: Flemming split his first pro season between Capitals AHL affiliate Hershey and the ECHL's South Carolina Stingrays. He opened the season with Hershey, playing in 21 games with the Bears before being sent to South Carolina at the end of December. Flemming scored 2 goals with 2 assists and was minus-three with 31 penalty minutes with the Bears. He was one of the Stingrays' top defenders; finishing plus-12 and scoring 2 goals with 10 assists and receiving 55 penalty minutes in 41 games. The Stingrays reached the second round after finishing fourth in the South Division. Flemming scored 2 goals (both on the power play) with 3 assists and was minus-four with 8 penalty minutes in nine playoff games.
Flemming is a two-way defenseman with offensive elements to his game. Despite less than ideal size for a defender, he is willing to compete in tight spaces and will drop the gloves when necessary. He is sometimes out-muscled due to his light frame and is not a particularly punishing player. The strength of his game is his ability to recognize plays and distribute the puck to open teammates. He was used in a forward role at times during his junior career with mixed results. Flemming was one of the top plus/minus players with Mississauga St. Michael's during his junior career. Flemming makes strong passes out of his own zone and is capable of handling power-play duties from the point.
Though Flemming is tall enough to be an effective defenseman, he still needs to add bulk and strength to compete with the bigger opponents in pro hockey. Flemming at this point is a decent two-way defensive prospect.