Not much went right for the Boston Celtics on Sunday night.

Boston was playing from behind for essentially the whole game before suffering an ugly 115-96 loss to the San Antonio Spurs at TD Garden.

The C’s were without Al Horford (knee), Jayson Tatum (back) and Robert Williams III (back) for Sunday night’s game, but got back Aron Baynes, who amassed nine points and eight rebounds on the floor. But it wasn’t enough as San Antonio came to play and secured the win.

Defensive woes and 3-point struggles weighed Boston down throughout the contest, and head coach Brad Stevens was in the locker room postgame for a longer-than-usual amount of time. After he emerged, he elaborated on what was said, noting there’s “frustration” amongst the team.

Stevens has said many times this season his team needs to play better, and with playoffs right around the corner, now is the time for the Celtics to step up their game if they want to have a lengthy postseason run.

Here are some other notes from Sunday’s Celtics-Spurs game:

— The Celtics had just eight assists in the first half, and 0-for-7 from distance in the first quarter.

Shots from deep hurt Boston throughout the game. The Green went just 7-for-34 for three in the contest.

— Marcus Smart led the C’s with 14 points.

Four other players reached double-figures for Boston, including Kyrie Irving who finished with a double-double.

— The loss marked the fourth straight for the Green, tying their longest skid of the season.

— Boston’s defense has been rough of late, to say the least, and Stevens has taken notice.