Through two games, Hayward is averaging 12.0 points and 6.0 rebounds in 24.5 minutes per game.
"We've got a spirited group that's ready to fight", Raptors coach Nick Nurse said.
Leonard played just 9 games last season for the Spurs due to a quadriceps injury.
Tatum did far more good than bad, finishing with 24 points and 14 rebounds as Boston held on to beat the New York Knicks 103-101 on Saturday night.
Leonard scored 31 points last night in the Raptors' 113-101 victory at Scotiabank Arena in Toronto. "You know, being from Jersey, and obviously envisioning myself as a free agent and ultimately taking a meeting and playing for [coach] Fiz and a great young core that they have here".
The Celtics looked sharp early in racing to a 26-10 lead Saturday and still had a double-digit cushion midway through the second quarter before Damyean Dotson's second straight 3-pointer trimmed it to 50-48 by halftime. Marcus Morris and Kylie Irving had 16 points apiece for Boston while Aron Baynes and Terry Rozier had 10 points each. Kanter became the first Knick since Zach Randolph (2007-08) to start the season with three straight double-doubles.
Knox was fouled driving to the rim on a fast break and rolled his ankle. The Knicks said X-rays for Knox are negative.
Knox was disqualified from the remainder of the game because he couldn't shoot the subsequent free throws. Hayward's season ended on opening night past year after he broke his leg in the first quarter.
Stevens added that there are no plans in place to rest Hayward regularly on the second night of back-to-back games.