Mantha underwent successful shoulder surgery Friday and will be out indefinitely, Samantha Pell of The Washington Post reports.
News of Mantha's shoulder surgery came just after it was announced he had been placed on injured reserve Friday. Mantha collided with defenseman John Carlson in the second period of Thursday's 5-4 overtime loss to the Panthers and did not return. The 27-year-old -- who has posted two goals and four assists in 10 games -- is expected to be out for a while, compounding a significant injury problem for a Capitals team already without Nicklas Backstrom (hip) and T.J. Oshie (lower body).