The team, who finished seventh in the Eastern Conference last season, opened their training camp at the start of this week.
The forward told the team's website: "We're in shape. I think that's a good start. I think our strength and conditioning guys did a great job training us for what's to come in pre-season and the whole pre-season [schedule].
"The coaches put us in the position we're in now, and that's being in good shape until the season starts."
The Celtics play the Toronto Raptors on Monday.