The National Basketball Association has suspended Paul George of the Philadelphia 76ers for 25 games without pay for violating the league’s anti-drug program.

The suspension took effect Saturday and will make George eligible to return on 25 March.

The NBA did not disclose the substance involved. In a statement released to ESPN, George said he took an improper medication while seeking treatment for a personal mental health issue and accepted full responsibility for the violation.

The penalty reflects a first offense under the NBA–NBPA agreement and is expected to cost the nine-time All-Star about $11.7 million in lost salary. The suspension will also slightly reduce Philadelphia’s luxury tax burden by an estimated $1.3 million.

George is averaging 16.0 points, 5.1 rebounds, and 3.7 assists in 27 starts this season. He missed the opening games of the campaign while recovering from left knee surgery and is currently in the first year of a four-year, $212 million contract with Philadelphia.

The 76ers entered Saturday with a 26-21 record, sixth in the Eastern Conference. Teammate Joel Embiid said it would be “impossible” to replace George’s impact as the team pushes toward the playoffs.