The NFL has suspended Baltimore Ravens defensive tackle Haloti Ngata for the final four games of the 2014 regular season after he tested positive for performance-enhancing substances, the team said Thursday. The league would not reveal which drug caused the failed test, but Ngata, 30, admitted in a statement that he knowingly ingested Adderall, a banned substance.

“I made a mistake, and I own this,” Ngata said, according to ESPN. “I took Adderall and take full responsibility for doing this. I am deeply sorry and broken up over this. I let down my family, my teammates, Ravens fans and myself. My hope is that the Ravens make the playoffs, and I believe they can do this. And, then I can come back and help us win.”

Ngata took Adderall to improve his focus, a bid to balance the demands of his football career and family life, a source told’s Ian Rapoport. The suspension will cost Ngata more than $2 million in game checks. His current contract with the Ravens runs through the end of the 2015 NFL season.

“This is disappointing news for the Ravens,” said Baltimore General Manager Ozzie Newsome, according to USA Today. “We are disappointed with Haloti, but not more than he is with himself.”

A five-time Pro Bowl selection, Ngata was in the midst of one of his most productive seasons for the Ravens. He recorded 32 total tackles, two sacks, two interceptions and a career-high seven-pass deflections in 12 games this season. Analytics website Pro Football Focus ranks Ngata as the league’s eighth-most effective defensive tackle in 2014, notes.

The Ravens are one of six AFC teams with a 7-5 record, but currently trail the Dolphins for the conference’s final playoff spot. Baltimore’s attempt to reach the postseason will continue without one of its top defensive players, though Ngata would be eligible to return to action if the Ravens earn a playoff berth.