(Photo credit: Winslow Townson-Imagn Images)

It was going well until it wasn't.

The second-seeded Boston Celtics took a 3-1 series lead over the Philadelphia 76ers in the NBA Eastern Conference quarterfinals. Six-time All-Star forward Jayson Tatum, who came back from Achilles tendon surgery much faster than anyone expected, was averaging 24.8 points through the first four games of the series.

But then the Sixers routed the host Celtics in Game 5 and Tatum hobbled off the court in the second half of Game 6, another Philadelphia triumph.

It was not apparent whether Boston coach Joe Mazzulla did not re-insert Tatum into Game 6 due to an injury or the fact that his team trailed by 23 points in the fourth quarter.

But Tatum's status for Sunday's Game 7 continued to downgrade and two hours before tipoff, he was ruled out for Boston's do-or-die contest.

Hence, the four-time All-NBA first-teamer sat on the bench in street clothes as the Sixers completed the comeback, ousting Boston 109-100.

Tatum addressed the media on Sunday, reflecting on his satisfaction on returning to the court and his frustration about the last few days.

'My recovery and comeback (from the Achilles injury) were going so well that how it ended, I didn't think it was going to end that way,' said Tatum. 'It was just unfortunate.

'I worked really, really, really, really hard to come back in the fashion that I did and play at the level I was playing at. So for it to end the way it did was a tough pill to swallow.'

Tatum explained that, since he was still in the return-to-play window, NBA protocols had to be followed pertaining to his left knee stiffness. The Celtics' medical team and Tatum's trainer, Nick Sang, agreed that he would not be able to compete on Saturday.

Tatum admitted on Sunday that he was not playing at full capacity since his return to the court on March 6 vs. Dallas. He rated himself at about 80-85% and relayed that his right leg is still shorter than his left.

The Boston star averaged 31.0 minutes per game in 11 March games and 36.2 minutes in five regular-season contests in April. His scoring (21.8) and shooting splits (41.1% FG, 32.9% 3FG) were a little below his career marks, but he rebounded at a career-best 10.0 per game heading into the playoffs.

But Tatum has no regrets about pushing himself to return in a 10-month window and help this year's team.

'I'm happy and proud of the fact that I was able to do that,' Tatum said. 'And, unfortunately, if somebody else has to deal with this, they can look at what I was able to do and have some hope and inspiration that it's not what people used to think it was. And you can come back from this and be who you were and hopefully be better.'

--Field Level Media