Tatum's totals of 27 points, eight rebounds and six assists weren't enough in the depleted Celtics' 111-107 loss to Golden State. Newly crowned 3-point king Stephen Curry led all scorers with 30 points on 5-of-14 shooting from deep.
Boston overcame a 20-point first-half deficit to take a fourth-quarter lead, but ultimately came up short. It was the Celtics' fourth loss in five games and quashed the momentum of a bounce-back win over defending champion Milwaukee on Monday.
"It wasn't about the scoring or slow start offensively, I think (it was) more so our defense and the hustle plays -- they out-hustled us, basically," Boston coach Ime Udoka said.
Starting center Al Horford and forwards Grant Williams and Sam Hauser were placed in COVID protocol earlier Friday. Celtics forwards Jabari Parker and Juancho Hernangomez landed in the protocol earlier in the week.
Boston guard Dennis Schroder also missed the Golden State matchup with a non-COVID illness.
"We fought -- that's really it," Smart said. "There's no moral victories. ... We lost."
New York is coming off a bounce-back effort in a 116-103 win at Houston on Thursday to snap a season-high four-game skid.
Immanuel Quickley paced an impressive Knicks' bench attack with a team-high 24 points. Mitchell Robinson added 17 points and Miles McBride added 15 with nine assists off the bench as just four New York reserves outscored Houston's six-man bench 63-36.
"They got going, so we ran with them a little bit longer," Knicks coach Tom Thibodeau said about his second unit. "I think it was good in some ways; it gave (Julius Randle) more rest, and it keeps him fresh down the stretch."
Evan Fournier scored 23 points on 8-of-12 shooting, and Randle finished with 21 points, six boards and six assists for New York.
The win came at a cost as starting guard Derrick Rose was ruled out with a right ankle injury after going scoreless on 0-of-2 shooting in 12 minutes. Rose is officially questionable for Saturday's game in Boston.
"Whoever we have, let's go," Thibodeau said about Saturday's game. "Safety's first, so whatever we have to do, we're going to do."
New York outlasted Boston in a 138-134 double-overtime thriller at home in the teams' first matchup of the season on opening night.
Randle's monster game of 35 points, nine assists and eight rebounds helped the Knicks survive a career-high 46-point night for Brown. Fournier added 32 points against his former Celtics team, Barrett scored 19 and Robinson had 11 with 17 rebounds.
Tatum totaled 20 points and 11 rebounds, Robert Williams III amassed 16 points, 10 boards and five blocks while Smart and Grant Williams scored 15 apiece in the defeat for Boston.
--Field Level Media