He played the small forward position for the Denver Nuggets, the Memphis Grizzlies, the Miami Heat, the Boston Celtics, the New Orleans Hornets, and the Indiana Pacers.

Posey won NBA championships as a member of the 2006 Miami Heat and the 2008 Boston Celtics, and as an assistant coach for the 2016 Cleveland Cavaliers.

After attending High School in Twinsburg, Ohio, Posey came to Xavier University in the 1995–96 season, but under Prop 48 rules, was ineligible, so sat out his freshman year.

He did all of that while not being a consistent starter in the Xavier lineup, almost always coming off the bench and Posey became well sought after from several sports agents such as Bill Duffy, Andy Miller, Craig McKenzie and Mark Bartelstein.

His rookie season, Posey averaged 8.2 points and 3.9 rebounds per game en route to being named to the all-rookie second team.

On March 29, 2004, Posey scored a career-high 38 points, including making a three-point shot to force a second overtime, during a 136–133 win against the Atlanta Hawks.

He had been a starter during the regular season, but head coach Pat Riley made the change of having Posey come off the bench for the playoffs.

As the Heat's sixth man, Posey was able to average 11.8 points per game on 48.8% shooting against Miami's first-round opponent, the Chicago Bulls.

Against Miami's second-round opponent, the New Jersey Nets, Posey was forced to play defense, particularly guarding Vince Carter or Richard Jefferson.

Posey again had to focus on defense against Miami's third-round opponent, the Detroit Pistons, particularly guarding Richard Hamilton, Tayshaun Prince, and even sometimes Chauncey Billups or Rasheed Wallace.

Posey's defense was able to take the pressure off of Miami's scorers like Dwyane Wade, Jason Williams and Antoine Walker so that they could focus on their strengths on the offensive end.

On the offensive end, Posey played a huge role in knocking down shots as a result of Miami's All-Stars, Wade and Shaquille O'Neal, being double-teamed and needing to pass the ball.

On August 25, 2007, Posey signed with the Boston Celtics, adding to their revamped roster, including newcomers Kevin Garnett and Ray Allen.

[9] On August 11, 2010, New Orleans sent Posey, along with Darren Collison, to the Pacers in a four-team, five-player trade with the New Jersey Nets and the Houston Rockets.

[24] Posey was suspended for the opener of the 2007–08 season by NBA commissioner David Stern after his no contest plea to reckless driving stemming from the DUI incident.