When Gordon Hayward suffered a gruesome injury in the season-opener against the Cleveland Cavaliers, the shock of the NBA world was evident instantly as social media exploded with well wishes for the star.

His peers know exactly how physically demanding rehabbing can be and the work required to get back to full fitness. The thought of surgery and a grueling recovery process can be awful for anybody.

But for a professional athlete, it can also take an emotional and mental toll as it could have a major impact on their career and how they perform once they return.

That has certainly been the case for Hayward as he has battled through the early stages of his rehab after the freak injury which ruined his Boston Celtics debut.

In a special interview on "The Dan Patrick Show", the small forward opened up about how his leg is not the only thing that hurts.

"It's been painful, but it's nothing like sitting around watching the team you were supposed to be playing with this year," he said.

"I signed to play for the Boston Celtics this year now to only sit and watch the Boston Celtics this year. That part has been difficult and much more difficult to deal with than the pain."

In a separate profile piece on Sports Illustrated, the All-Star spoke at length about how difficult it's been for him to watch the C's.

According to Lee Jenkins: “If the Celtics were winning, (Hayward) felt sorry for himself, because he was missing out. If they were losing, he felt sorry for everybody else, because he couldn’t help.”

By all accounts, the 27-year-old's rehab is going well and recently removed his walking boot, which was a significant step.

Both the team and Hayward are not putting a timetable on his return but he retains some hope that he could make a comeback before the end of the season.

"I work out every day to try to increase my range of motion and increase my strength in my legs so that I can be back as fast as I can," he said.

"Whether that's this year or this summer or next year, I will just let that happen. But for sure, as a competitor, I'm just trying to come back faster than anyone has ever done it."

It would represent a remarkable recovery if the former Utah Jazz man is able to return at some point this year. With the Celtics primed to make a deep playoff run and compete for a championship, his presence could be a huge boost.