The good news for the Celtics is they return home just 4½ games behind the Cavaliers for the best record in the East, and they left for the trip 6½ back. Even after that disappointing loss to the Lakers, the only blemish on the trip, there was still optimism that improvement was ongoing.

And that was evident when the Celtics dominated the final three quarters to handle the Mavericks in an NBA Finals rematch, as they received rare strong offensive games from Derrick White and Jrue Holiday together. And it seemed they have come to the realization that they’ll need to change their offensive approach because they’re being defended differently this season.

Celtics coach Joe Mazzulla acknowledged teams are being more physical and aggressive with his club, taking more chances and putting pressure on White and Holiday to shoot instead of distribute.

“Obviously I think physicality is up as a league in general,” he said. “I think we’re being cross-matched [teams seeking mismatches or using a bigger player to defend a smaller player] more than we have in the past. We had some phases of that last year in spurts, in the playoffs but I think the physicality is up.

“That takes time to recognize. [The Mavericks] have a great defensive coach, great defensive scheme here, and [the] game starts and the first five or 10 possessions we’ll have an understanding of [what] those are. Sometimes the scout starts when the game starts because of the type of talent that we have. We have to pick up on that and get to that fast. That’s the space we’re in and it’s good for us to go through it.”

The response to changing defenses is banking that players other than Tatum and Jaylen Brown can flourish against these cross matches. It’s finding spots where White and Holiday can get open threes, where Porzingis can post up and get defenders in foul trouble.

The issue has been that physical defense play has been encouraged more by the league this season. Buckets are harder to come by and Boston’s shooting numbers have dipped from 48.7 percent from the field last season to 45.6 this year and from 38.8 from the 3-point line to 36.4.

“We have matched [the physicality] in spurts,” Mazzulla said. “I think [Porzingis’s] presence on the offensive end of the floor versus switching the last few games has been big time for us. He’s played with a high level of physicality on both ends. I think it starts with him. It’s the way we go about paint points. It’s the way we go back to attacking switching. It’s the way we go about owning space and fighting for position.”

So, in other words, the Celtics are just going to have to be tougher and grimier than before, because the league is adjusting. They can’t do it overnight but they are progressing. And they still possess the third-best record in the NBA despite their recent troubles. They’ll face No. 4 on Monday in the Rockets, who did Boston a favor by knocking off the Cavaliers twice this week.

Toughness for the Celtics also means responding favorably in the first home game back from a long road trip, a situation in which they struggled mightily a few weeks ago against the Kings.

Written on the white board in the Celtics’ locker room in Dallas was an apparent quote from Brown that said: “We want to make sure we come together and look at each other in the eye and put our best foot forward. You see a lot of teams won’t do that.”

After the victory, Brown looked over at the quote with cynicism because he doesn’t remember saying it. But wherever it came from, it did capture the coherent theme that the Celtics have to stay cohesive during what has been a trying season so far.

“After a loss, we’ve always got ourselves back together and it’s a new day,” he said. “We’re in the middle of the season and things have gone the opposite way for us. But we’re still second in the East and I feel like we’ve got a lot of good basketball in front of us.

“The most important thing for us is to let these things be learning experiences. Don’t let it break our spirit. We’re due for a lot of makes. We know what it takes to win over here, so we’ve got to keep building those steps every single day.”

Save the clunker against the Lakers, the Celtics did take those necessary steps forward over the past week. They’ve realized they can’t do the same ol’ thing as last year and expect the same results. They’ve been staggered at times by how they’re being played and guarded, and it’s time they begin punching back more consistently and turn themselves into a true championship caliber club again.

Gary Washburn is a Globe columnist. He can be reached at gary.washburn@globe.com. Follow him @GwashburnGlobe.