The Boston Celtics (43-21) finally got a real look at their lineup with Jayson Tatum back in the mix - and the early returns were extremely encouraging.

Boston erased an early deficit and dominated most of Sunday’s matchup against the Cleveland Cavaliers (39-25), pulling away for a 109-98 win at Rocket Arena.

After falling behind 11-3 in the opening minutes, the Celtics seized control with a suffocating defensive stretch that turned the game into a rout long before the fourth quarter.

Boston closed the first half on a massive 53-25 run, holding Cleveland to just 28.9% shooting and an astonishing 2 for 22 mark from three-point range before halftime.

Even though the Celtics shot only 39% from the field themselves in the first half, their defense created a 20-point cushion that Cleveland never seriously threatened.

Jaylen Brown led Boston with 23 points while Tatum added 20 points in 28 minutes during his second game back from an Achilles tear. Payton Pritchard provided a major spark off the bench with 18 points and 7 assists. Cleveland was paced by Donovan Mitchell, who finished with a game-high 30 points.

With the victory, Boston completed a season sweep of Cleveland - the first leg of a three-game road trip that will next bring them to face the San Antonio Spurs (46-17) on Tuesday.

Here are four takeaways from Sunday’s win:

Even on a minutes restriction, Tatum wasted little time asserting himself.

The Celtics star logged 28 minutes and came out aggressively, scoring 12 points in the first quarter alone while attacking Cleveland’s defense in a variety of ways.

Tatum mixed pull-up jumpers with strong drives to the rim, including several finishes through contact against Evan Mobley.

The three-point shot wasn’t falling - Tatum struggled to find rhythm from beyond the arc and missed several perimeter looks after his strong opening quarter.

Still, his overall impact remained clear as he finished with 20 points and helped keep Boston’s offense organized.

Most importantly, he looked physically comfortable.

For a player returning from a lengthy injury absence, that’s the biggest takeaway of all.

The Cavaliers simply could not buy a basket in the second quarter.

Cleveland managed just 10 points in the entire frame and scored only two points over the first 7:21 of the period.

The Cavaliers shot 4 of 25 from the field, and missed all 14 of their three-point attempts during the quarter.

Aside from Mobley and Mitchell, Cleveland’s roster combined to shoot 0 for 15 in the period.

That brutal stretch allowed Boston to completely flip the game.

What started as an early deficit quickly turned into a comfortable halftime lead that the Celtics never relinquished.

One of the biggest ripple effects of Tatum’s return is that several players are sliding back into smaller roles - and those players are thriving.

Boston’s bench outscored Cleveland’s reserves 19-2 in the first half and remained impactful throughout the afternoon.

Pritchard was especially important, finishing as a plus-18 in 32 minutes while orchestrating the offense for long stretches.

Baylor Scheierman also delivered one of his strongest performances of the season, recording a double-double and knocking down key shots as Boston built its lead.

During a crucial third-quarter stretch, Boston went on a 16-2 run with Tatum and Derrick White both on the bench - a testament to how deep and balanced the Celtics roster remains.

Many expected a lengthy adjustment period once Tatum returned from his injury.

So far, that hasn’t happened.

Boston has looked sharp in the early stages of Tatum’s return, with the star forward already playing close to 30 minutes and the team’s supporting cast continuing to excel in more natural roles.

Sunday’s game was also a useful measuring stick against a legitimate Eastern Conference contender.

The results were convincing.

Boston controlled the game defensively, dominated the bench battle, and ultimately showed a level of depth that few teams in the conference can match.

If Tatum continues to ramp up without setbacks, the Celtics’ margin for error in the East may become very small.

For the rest of the conference, that’s a troubling sign.

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Tom Carroll is a contributor for Roundtable, with boots-on-the-ground coverage of all things Boston sports. He's a senior digital content producer for WEEI.com, and a native of Lincoln, RI.