Known as "Slammin' Sam" during Lacey's college career, the 6-foot-10, 240 pound center was a powerhouse on the boards. His rebounding and scoring helped the Aggies achieve a combined 74-14 record and reach the NCAA Tournament all three years he played. During the 1969-70 season he averaged 17.7 points and 15.9 rebounds, leading New Mexico State to their first and only Final Four appearance. In 1968, he was the MVP of the Evansville Classic. Lacey holds school records for single-season rebounds (493) and rebounds per game (15.9), as of 2024. In 1975, he was inducted into the New Mexico State Athletics Hall of Fame. In February 2008, Lacey was among the first inductees into the Aggies Ring of Honor and in 2015, he became the first New Mexico State basketball player to be inducted into the New Mexico Sports Hall of Fame.

Professionally, Lacey was the fifth overall pick in the 1970 NBA Draft by the Cinncinati Royals. He played 13 seasons in the NBA, amassing 10,303 points (10.3 PPG), 9,687 rebounds (9.7 RPG), and 3,754 assists (3.7 APG). At his induction in 2024, Lacey ranked 45th overall for total rebounds in NBA history, and 49th on combined ABA/NBA total rebounds.

Died March 14, 2014, at age 65