Though he has since recovered from that injury, Hayward told reporters Wednesday that he's been dealing with back soreness.
"My back's been ongoing a little bit, but definitely got progressively worse and that's what made me think I need to dial it back a little bit. I think in the past, it's bothered me, but it's gone down with treatment and stuff. But this time it was getting worse, especially after playing. So, like I said, I have to rebuild the strength. My leg is strong because I've been focusing on that. But then you forget that you don't focus on other things that are important and the back is definitely an important part. You can't do much when your back is hurting."
Part of dialing it back was missing Saturday's preseason loss to the Cleveland Cavaliers.
Hayward did declare Wednesday's practice was "encouraging" and said it was the "best I've felt since I've been here yesterday." He also said he plans on playing in Tuesday's season opener against the Philadelphia 76ers—the team Boston eliminated in the second round of the playoffs and a legitimate challenger in the Eastern Conference.
The back is a newer concern, though, after he underwent surgery in May to remove the plate and screws from his leg.
A healthy Hayward would give the Celtics a weapon they didn't have last season when they reached Game 7 of the Eastern Conference Finals before losing to the Cavaliers. Hayward averaged 21.9 points, 5.4 rebounds and 3.5 assists per game while shooting 39.8 percent from deep in 2016-17 on the Utah Jazz.
Boston proved it was loaded with playmakers last season when it took LeBron James and Co. to a decisive game with Hayward and Kyrie Irving sidelined. Getting both Irving and Hayward back alongside Jayson Tatum, Jaylen Brown and Al Horford has led to a Finals-or-bust mentality for the Celtics, especially given James' decision to sign with the Los Angeles Lakers.
Boston's most important games of the season will happen in April and beyond, so it's wise for Hayward to dial things back in October. It's far more important that he remains healthy throughout the season than it is for him to thrive in the opening few weeks.