Watch Celtics’ head coach Brad Stevens speak on Boston’s defensive struggles after their 10th loss of the season against Dallas.

Coming into the 2018-19 NBA season, the Boston Celtics were predicted to have one of their best seasons yet. The Eastern Conference was supposed to go through them. However, 20 games into the season and the Celtics are sitting at .500 with a 10-10 record after their loss to the Mavericks, 114-103, on Saturday. Last season, the C’s didn’t suffer their 10th loss until the 37th game of the year.

To start the fourth quarter, the Celtics only trailed by five, but the Mavericks pulled away with key three-pointers and a timely run. Dallas extended their lead 106-90 after multiple three-pointers from JJ Barea and Wesley Matthews with under five minutes left in the game. The Mavericks’ 16-point lead was enough to seal the win at American Airlines Center.

“At the start of the fourth (quarter), they had a few things go their way. They made a ton of effort plays. They got a bunch at the rim. And we couldn’t contain the drive,” Stevens said. ” Obviously, you saw the discouragement at the end.”

The Celtics are giving up four more points per game (104.3) than they did last season. After Saturday’s loss, the Celtics have now allowed 100 or more points to the opposing team 14 times this season.

“We were a step slow all night. I thought they (Mavericks) put us on our heels, and they were moving the ball – whipping it around – and they were running their stuff with great pace,” Stevens said.

While the Celtics have lost four of their last five games – with two of their losses coming against non-playoff teams last seasons, such as the Knicks and Hornets – they are still in the thick of things. They are currently in the sixth seed in the East.