To put it mildly, the Boston Celtics have been a disappointment so far this season.

Expected to be the class of the Eastern Conference, the C’s have limped out of the gate, compiling an 11-10 record through 21 games.

Boston’s offense has been a disjointed mess all season. The Celtics haven’t been getting to the rim or the free-throw line. They’ve also been hoisting 3-pointers at a ridiculous pace (35.9 per game) but haven’t hit them with any regularity, connecting on 35.9 percent of their looks from deep.

After losing to the Dallas Mavericks on Saturday, point guard Kyrie Irving noted the C’s were almost at the “rock bottom point where the team could blow up.”

So what’s been holding Boston back this season? If you ask former NBA star Jim Jackson, the answer is Gordon Hayward.

Jackson was a guest on FOX Sports 1’s “Speak For Yourself” on Tuesday and explained how the forward’s reintegration into the lineup is causing the Celtics to struggle offensively.

Hayward missed all but five minutes of last season after suffering a dislocated ankle and fractured tibia. The Butler product has been tentative in his return, leading to a move from the starting lineup to the bench.

While he still has yet to find consistency with his jump shot or the fearlessness to attack the rim with reckless abandon, Hayward has settled into a role as a facilitator off the bench and has looked better offensively over the past week, which should give Celtics fans some hope.

Boston’s problems go well beyond Hayward, though.

Jayson Tatum struggled to open the season, as the young forward fell into an isolation hole that saw him take a number of long 2-point shots and fail to move the ball within the offense. While Boston’s defense is ranked highly, it has been scorched by opposing guards this season, giving up big scoring nights to Jamal Murray, Devin Booker, Trey Burke and J.J. Barea in recent weeks.

The bottom line is this: Gordon Hayward might be the least of the Celtics’ worries.