Petrie scored 1321 points in college, third in school history at the end of his career in 1970 and still seventh after the 2009–10 season. His 541 in 1968-69 was fourth to each of Bill Bradley's single-season totals until Brian Taylor moved him down to sixth where he still stands. He continued to rank fourth in school history with a 18.3 points/game average through the 2009–10 season. His 1969–70 single season average of 22.3 is sixth behind only Bradley and Taylor and his 20.8 average the prior year stands eighth. His 530 career field goal stands fourth on the school list behind Bradley Kit Mueller and Craig Robinson. 216 field goals in 1968–69 ranks fifth behind Bradley and Taylor, while his 189 the following year ranks eighth. 17 made against Fordham, January 26, 1970 trails only Bradley's three best nights.
At 6'4" he could play either guard or forward positions and was a long range shooter. He played in two All-Star games and in 1971, the Blazers' first year in existence, was named co-Rookie of the Year with the Boston Celtics' Dave Cowens after averaging 24.8 points per game. Until Damon Stoudamire's 54 point performance in 2005, Petrie held the Blazers' individual scoring record for one game at 51 — a feat he accomplished twice. His jersey number, 45, was retired by the Blazers. Following the 1975–76 NBA season he was traded to the Atlanta Hawks in a transaction that landed Portland Maurice Lucas. Petrie did not play any games for the Hawks after suffering a career-ending knee injury.
Petrie is credited as the first NBA player to switch from Converse brand athletic shoe, which were popular in the 1970s, to Nike brand.
Petrie worked in the private sector for several years after leaving the NBA, and in 1985 began working for the Blazers. He worked as a commentator for Blazer radio broadcasts and several other positions before being hired as senior vice president for operations. He left Portland in 1994 and was hired by Sacramento as president of basketball operations. As an executive he won the NBA Executive of the Year Award twice with the Sacramento Kings, first in 1999 and again in 2001.
On December 29, 2009, Petrie received a three-year extension as team president through the 2012–13 season.