It didn’t take the Celtics long to lock up two of their few internal free agents.

Minutes after the official start of NBA free agency Sunday evening, ESPN’s Adrian Wojnarowski reported center Luke Kornet had agreed to terms on a one-year contract to remain in Boston.

One hour later, The Athletic’s Shams Charania reported the Celtics also had reached an agreement on a multi-year deal with center Neemias Queta.

Together, the re-signings of Kornet and Queta helped shore up Boston’s frontcourt depth behind Kristaps Porzingis and Al Horford, which will be necessary with Porzingis expected to miss at least the first month of the 2024-25 season following leg surgery. The moves also ensured the Celtics will retain nearly their entire core from their NBA championship run.

With Boston also exercising its team option for reserve wing Sam Hauser on Saturday, the team’s top nine players in terms of minutes played in 2023-24 are under contract for the upcoming season.

The 7-foot-2 Kornet was the Celtics’ third center behind Porzingis and Horford this season, appearing in 63 regular-season games with seven starts. A 28-year-old journeyman who previously spent time with New York, Chicago, Cleveland and Milwaukee, Kornet set career highs in rebounds per game (4.1) and field-goal percentage (70%) for the champion C’s.

Kornet also logged vital minutes during the playoffs, often serving as Boston’s top reserve big man while Porzingis was sidelined with a calf injury.

Queta, a second-round pick by Sacramento in 2021, split his first season in Boston between the Celtics and their G League affiliate in Maine. The 24-year-old saw action in 28 games off the bench for the big club, averaging 5.5 points and 4.4 rebounds per appearance.

Queta was not part of head coach Joe Mazzulla’s postseason rotation, making just three garbage-time appearances during Boston’s run to Banner 18. But he showed enough promise during the season that the Celtics promoted him from a two-way player to their 15-man roster in April.

The Celtics declined Queta’s team option on Saturday, making him an unrestricted free agent, but re-signed him one day later.

“Everybody on our roster, we love having here,” president of basketball operations Brad Stevens said Thursday in his post-draft news conference. “We’ll continue to work on filling out our roster for the upcoming season, but there’s no doubt that we’ll really value continuity of that.”

The 2024-25 Celtics will indeed look very similar to the team that brought the Larry O’Brien Trophy back to TD Garden. Once it officially signs first-round draft pick Baylor Scheierman, Boston will have just two available 15-man roster spots for potential newcomers.