Now, MLS’s renaissance man is embarking on a new journey.

The D.C. United defender, in his 12th pro season, is retiring because he wants to become a doctor.

Russell, who turns 34 this summer, is beginning post-graduate work at Georgetown University, beefing up his math and science portfolio, and plans to enroll in medical school in about 18 months.

Russell and the team are expected to discuss his decision sometime today. (See update below.)

After appearing in 19 of 34 league matches last season — his first in Washington after 3 1/2 with Real Salt Lake — he re-signed with United in December with the intention of playing probably one more year.

Russell has entered just one of 10 matches, however, a six-minute stint at the end of United’s 3-2 loss to the Philadelphia Union on April 21 at RFK Stadium. It was becoming clear early on he was not in the club’s immediate or long-term plans. So instead of waiting another year to open a new chapter in his life, he approached United officials about stepping away.

Russell’s departure will open a roster slot and clear a bit of salary cap space for a 1-8-1 team seeking help amid the worst start in its 18-year history. (Russell had taken a pay cut over the winter and was set to earn $75,000, according to MLS players’ union documents.)

Russell’s primary position is right back. Frankie Simek, a former U.S. national team right back who has spent his entire career in England, began a trial with the team Tuesday. The club also plans to address several other positions in the coming months.

UPDATE: Russell’s retirement is now official. He practiced today and will remain active for the rest of the week before turning full attention to Georgetown University’s Post-Baccalaureate Pre-Medical Program.

“I’m very happy with my career – so, I’m just looking forward to going back to school, a little bit scared, but it’s really exciting and it’s a lot of fun.”

A complete story will appear in Thursday’s print edition (available online later today).