As good as the Celtics were last season, they proved to be maddeningly frustrating at certain times.

Both in the regular season and playoffs, they routinely lost games they shouldn’t. They made a habit of playing down to inferior opponents.

Monday night in Washington, D.C., would have been a prime example. After two exciting, high-profile victories against the Knicks and Heat to start the season, last season’s Celtics may have suffered a letdown against the rebuilding Wizards.

Not so much this time.

In what may be a sign of the Celtics’ improved maturity, they handled business easily. Jaylen Brown scored 36 points and Jayson Tatum had 33 – both in just three quarters – as the C’s blitzed the Wizards from the opening tip and never looked back in a dominant 126-107 victory that was more lopsided than the final score indicated.

The Celtics led 37-11 at one stage in the first quarter, scored 77 points in the first half and led by as many as 37 points late in the third quarter as they had absolutely no problem against the Wizards’ porous defense. Leading by 33 entering the fourth, Celtics coach Joe Mazzulla pulled his starters.

The C’s are now 3-0, marking the first time they’ve had such a start in back-to-back seasons since 1976 and 1977.