The Boston Celtics handed the Cleveland Cavaliers their first defeat of the season on Tuesday, holding off a spirited fightback to record a thrilling 120-117 victory.

It is not easy to go on a long winning streak, and even harder to pull one off that manages to go into double digits to start the regular season. The Cavs have roared out of the gate to do both, causing NBA fans and analysts alike to begin asking if Cleveland is really a legit threat to Boston in the East.

The defending NBA champions held off the league’s hottest team, with Jayson Tatum scoring 33 points and adding 12 rebounds to lead the Boston Celtics to a 120-117 victory over Cleveland and hand the Cavaliers their first loss after 15 straight wins to open the season.