The ear-to-ear grin on the face of Boston Celtics big man Robert Williams III was undeniable following his Wednesday morning workout.

Taking a quick peek at the calendar, you can understand why.

When Williams underwent successful surgery on September 23 to “remove loose bodies and address swelling" from his left knee, the best-case scenario was that he would be back to playing in eight weeks, or what we like to call Friday of this week against the New Orleans Pelicans.

Williams is being coy about his return to the floor, other than to say that he and the medical staff are continuing to “check off the boxes” for things he needs to do in order to be cleared to play.

But there’s no mistaking the excitement that he’s feeling now, well aware that he’ll be back on the floor sooner rather than later.

“(Wednesday’s workout) felt good, felt great,” Williams told me during our one-on-one interview. “That’s why I’m smiling. We’re checking off all the boxes as I go through this, getting closer to getting back.”

And today was indeed a good day as Williams described his on-court session work being the most game-simulation work he’s done since he began the rehab process.

The time Williams has been sidelined has not had a significant impact on the Celtics’ success, with Boston having extended its winning streak to eight in a row with Wednesday night’s blowout win over the Atlanta Hawks.

But the Celtics know all too well that their chances of getting back to the NBA Finals and emerging with the Larry O’Brien trophy this time is greatly enhanced with a healthy Robert Williams in the lineup.

“Rob is a very important, a big piece to our play last year,” Marcus Smart, the NBA’s Defensive Player of the Year last season, said during a one-on-one interview. “We’re glad he’s taking his time, getting back on the court and taking those baby steps to get back on the court, getting closer, it’s a big improvement and boost for us.”

Williams’ emergence last year was instrumental in Boston’s ascension to the NBA Finals. A late-season injury sidelined him and left his return during the Finals in doubt. But Williams managed to return for most of Boston’s postseason run, playing in 17 of the Celtics' 24 postseason games last season. But it was clear that the All-NBA Defensive First Team big man was not the same, showing clear limitations in his mobility and with that, minimizing the impact he and the Celtics had grown accustomed to him making when on the floor.

That’s why his return after a lengthy layoff to start the season is so important.

The way Williams sees it, he’s used to missing games during the regular season.

This year, the only difference is he’s getting it out of the way at the start rather than in the heat of the season or playoffs.

And while Boston has managed to put together the best record in the East, the team’s overall defense has taken a noticeable hit during his absence.

Boston, which had the league’s best defensive rating last season, has been working its way out of the doldrums of being among the NBA’s bottom 10 in most defensive categories.

I spoke with Jaylen Brown about the importance of having Williams in the lineup.

“Rob takes our game to another level offensively and defensively,” Brown said. “He’s a game-changer out there. It makes us stronger and better.”

And the Celtics will see Williams’ impact back in the lineup on … when are you coming back, Rob?

“Can’t speak too much on that,” Williams told me. “We’re trying to check off these boxes, week by week. All I can do is smile right now.”

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