Following the game, Hathaway explained the incident to reporters: "Unfortunately, spit came out of my mouth after I got sucker-punched, and it went onto him. It has no place. It was an emotional play by me. You don't plan any of that stuff in your head, and it was a quick reaction and unfortunately the wrong one for me to a sucker punch."
Cameras clearly showed Hathaway spit in the direction of Gudbranson, which elicited a heated response from the blueliner:
Hathaway received a five-minute match penalty, which carries an automatic ejection from the game. Washington was leading 3-0 at the time of the penalty late in the second period, and it managed to both kill off the penalty and hang on to win the game.
After Hathaway assisted on a goal from Chandler Stephenson that made the score 3-0 in favor of Washington, a wild brawl broke out that involved several Ducks players, including Gudbranson, Derek Grant and Nick Ritchie, the latter of whom was also ejected.
Gudbranson made it clear after the game that he didn't appreciate Hathaway's actions: "That's about as low as you dig a pit, really. It's a bad thing to do. It's something you just don't do in a game, and he did it."
The 27-year-old Hathaway is in his fifth NHL season and his first with the Caps. He has seven points through 23 games as a fourth-line depth player, which has him on pace for his most productive offensive season to date.
A suspension could be forthcoming for Hathaway, although it likely wouldn't have a major impact on a Capitals team that tops the NHL by a wide margin this season with 36 points.
Alex Ovechkin, John Carlson, Evgeny Kuznetsov, Jakub Vrana, Tom Wilson and Nicklas Backstrom are all enjoying huge offensive seasons for the Caps, so they have more than enough firepower to overcome the temporary loss of a bottom-six forward.
As for the newly formed Caps vs. Ducks rivalry, they are scheduled to meet again Dec. 6 in Anaheim. The relatively short turnaround time between meetings means there could be some residual bad blood.