BOSTON — The Celtics were working on out-of-bounds sets at Monday’s practice when coach Brad Stevens sidled up next to Robert Williams and asked the rookie about the jaw-dropping alley-oop he threw down for his first NBA points in the fourth quarter of Saturday’s win in Detroit.

It turns out Williams messed up the play.

“Coach told me it was supposed to be a comeback screen and I was supposed to turn around and go screen again,” Williams said with a sheepish grin. 

After initially screening for Gordon Hayward, Williams saw a clear path to the rim and rumbled towards the basket as Marcus Smart sent a big lob that Williams caught above the charge circle before throwing down a vicious two-handed slam as Boston’s entire bench spilled onto the floor in celebration.

“[Stevens] said, ‘Rob, it’s alright if you run the play wrong as long as you jump 13 feet in the air and dunk it,’” Williams said with a chuckle. "So if I’m gonna [mess] it up, I gotta be prepared to dunk it.”

Stevens confirmed that Williams went off script, but he’s OK with some freelancing if it ends the way it did that night. Said Stevens: "I told him, ‘You can run them all wrong if you dunk it at 13 feet."

    Logging his first extended regular-season minutes on Saturday, Williams offered a tantalizing glimpse of his potential, not only with the loud alley-oop but with three blocks, two rebounds, and one fancy assist over eight minutes.


    The 6-foot-10 Williams could be in line for more playing time after the Celtics announced Monday that second-year big man Daniel Theis will be sidelined indefinitely due to plantar fasciitis in his right foot.


    Boston should get a frontcourt reinforcement Tuesday with Aron Baynes, sidelined the past three games due to a sore right hamstring, expected to return. But if Baynes’ minutes are limited and Theis is out, then Boston’s only other pure bigs behind starter Al Horford would be Williams and Guerschon Yabusele. 

    Williams has played just 11 total minutes through six games and will be asked to learn on the fly but Stevens has complete confidence in the No. 27 pick in this year’s draft. Especially because of the unique athleticism he brings to the court.

    "The vertical athleticism, that vertical separation, is what people are looking for off pick-and-rolls. Then on the [defensive] end, that's where [his athleticism] can be really effective,” said Stevens. "He’s gotta have an expeditious learning curve with not playing as much early.

    “But I have no doubt he could be thrown in when it’s all on the line.”

    That’s a particularly bold statement considering how most expected Williams to toil in Maine with the G-League Red Claws given Boston’s depth and the rookie’s need for game reps. Williams missed much of summer league with knee tendinitis and played only 40 total minutes in the preseason.

    Williams is such a freak athlete that he gives the Celtics a jolt of something they have long lacked, and moments like that loud alley-oop — improvised or not — might strengthen Williams' case for additional court time.

    But even his mother is giving him grief about messing up that play, among others.


    “S---, really just a bunch of criticism on the s--- I did wrong,” Williams said Monday when asked how his family and friends reacted to the highlight-reel alley-oop. "My mom got on my a-- about the angles of the screens I was setting. Hey, it's tough love, it’s what I need.”

    Williams has gotten plenty of advice after making a less-than-stellar first impression in Boston. Williams, a projected lottery talent, didn’t attend the draft in New York, electing instead to be with friends and family at a Buffalo Wild Wings in his native Louisiana. The next morning, he overslept a conference call with Boston reporters.

    After a more formal introduction at the team’s sparkling new practice facility a few days later, Williams missed a flight and was absent for the team's first summer league practice of the season.

    Otherwise, he’s been a model student, soaking up all he can from veterans like Al Horford. The Celtics assigned coaching assistant Alex Barlow to work with Williams, who even rented a place within walking distance of the Auerbach Center in Brighton so that he could ensure on-time arrivals.

    Asked what has stood out about Williams’ development since draft night, Stevens said, "Just his desire to be better.” Then he wondered out loud if missing that first practice might have been a blessing in disguise for Williams.


    "Missing the first practice probably was a good thing now, in retrospect,” said Stevens. "Because I think that it even locked him in more so. I think his work ethic has been awesome. His spirit is great. He and Barlow have a fun relationship. 

    "I’m really glad he’s here. I think he’s got a high upside.”

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