According to Mathias Brunet of La Presse, Brassard announced Sunday that his playing days are over.
Brassard had surgery on a broken fibula Saturday and will miss the remainder of the season, per Bruce Garrioch of the Ottawa Sun.
Brassard logged a goal on two shots in Monday's 5-2 win over the Panthers.
Brassard supplied an assist in Friday's 4-3 overtime loss to the Blackhawks.
Brassard netted a goal in a 6-2 win against Toronto on Friday.
Brassard scored a goal on his lone shot in Tuesday's 4-0 win over Columbus.
Brassard scored a goal and added an assist in Friday's 5-1 win over Anaheim.
Brassard scored a second-period goal during Saturday's 5-1 defeat to the visiting Devils.
Brassard scored in his first game of the season Monday as the Senators upended Dallas 4-2.
Brassard will move into Ottawa's top-six forward group because of Josh Norris' absence due to injury, TSN 1200 Ottawa reports.