After late loss to Sixers, the question remains … What happened to the Celtics’ elite defense?

(Mitchell Leff/Getty Images)

Ever since Brad Stevens has had some talent (ie. post-2015) to work with at the NBA level, his teams have primarily been stellar on defense. Boston has had a top-five defense for two of the past three regular seasons and they still rank sixth overall this year on paper, allowing 104.7 points per 100 possessions.

Yet, even ahead of the Celtics surrendering 118 points to the 76ers on Wednesday night, Stevens was not a believer in his team’s defensive prowess even as the numbers that indicated that this team was well above-average on that end of the floor.

“I still can’t believe where we’re ranked, that’s not what my eyes tell me,” Stevens explained. “I still don’t think we’re as good a defense as our ranking. It’s something that we really need to improve in the next month.”

Stevens' eyes do not deceive him. For the past two months (since February 1st), the Celtics have been the 20th-best defense in the NBA, allowing 109.6 points per 100 possessions, five points worse than their season average. They are the worst defensive playoff team in the league over that stretch and they’ve been consistently this bad for nearly a third of the season (21 games). To make matters worse, they have been even worse in the fourth quarter than full games over that stretch. Their defensive rating balloons to 112 points per 100 possessions in the final frame (seven points worse than their season average), which has been a crucial factor in the team’s pedestrian 11-10 record since February 1st.

There have been all kinds of contributing causes to the defensive dropoff during this span from injuries (Aron Baynes) to effort issues (Kyrie Irving pre-plane ride) to periodic lapses (Jaylen Brown, Jayson Tatum against Denver). However, one major glaring issue continues to slide under the radar, at least when it comes to minutes distribution and this problem was on full display throughout the fourth quarter of Wednesday’s loss to the Sixers.

The issue? Marcus Morris has been dragging down Boston’s defense on a nightly basis for the past couple of months.