PHILADELPHIA — It was nice of the Philadelphia 76ers to join the fray of this Eastern Conference semifinals series, four games in. Though there actually was nothing nice about it.

After two games in which the Sixers might as well have been playing in Portland in January, they finally found their playoff gear Sunday and ground it with a vengeance. Philadelphia came hard, with force, with intensity, with bruising, physical play. It jumped on Boston early in every way, and even though the initial lead didn’t hold up, messages got sent and a line had been drawn on the hardwood.

“You know, they set the tone for how the game is gonna be officiated,” said Boston’s Jaylen Brown, who looked as if he were playing 1-on-5 in the game’s opening minutes. “It worked. Tougher teams set the rules and tonight that was them.”

The Sixers’ first serious dig-down of the series, along with their Game 1 victory driven by the adrenaline and desperation of missing center Joel Embiid, has this even at 2-2, with Game 5 set for Tuesday at TD Garden (7:30 p.m. ET, TNT) and Game 6 assured back at Wells Fargo Center Thursday (7:30 ET, ESPN). The Celtics’ home-court edge is intact, but to play off Philly coach Doc Rivers’ motivational tactic over the weekend, this best-of-seven is as close as it can be four games in.

“We’re in a bar fight,” Rivers said Sunday evening, “and we’ve got to keep slugging.”

Here are five takeaways from Philadelphia’s 116-115 overtime thriller that will be back in, and worthy of, prime time:

1. No more ‘Ben’ Harden — or was it James ‘Simmons?’

Harden, the one-time MVP and three-time scoring champion, was a mess in Games 2 and 3 after stirring those echoes in the series opener. By Friday’s loss, he even was passing up shots like Ben Simmons, the offensively insecure former No. 1 pick who got shipped out of town for precisely that bad habit.

Virtually everyone and everything was challenging Harden to snap out of it heading toward Sunday’s matinee: tough Philadelphia sports media, cranky fans, Rivers, Embiid and the ugly numbers he was posting when guarded by Brown and some Boston cohorts. And just when you wondered whether he might prefer to be in Las Vegas or Cancun, The Beard snapped back to reality in stark relief.

Harden hit seven of his first eight shots to be very much in the moment. He scored 18 points in his first 13 minutes. He hit 16 of 23 shots overall, six of his nine 3-pointers, and was into his 48th minute when he drained the game-winner from the right corner with 19 seconds left in overtime.

He shrugged off suggestions that he locked in or even played any better Sunday than in the previous two, but that was silly. Of course he did. With 42 points, he and Embiid (34) accounted for two-thirds of the Sixers’ scoring. The two future Hall of Famers made 55% of their shots, while their six teammates totaled 40 points on 36% shooting.

2. Thrills ensue late in Game 4

Rivers dropped that term the other day for what a playoff series can wreak on those involved. Nerves and gut checks clearly were on display in Game 4.

Philadelphia grabbed, then lost, its quick opening lead. Then it pushed in front, opening a gap of 16 points a couple times in the third quarter and still leading by 10 as the fourth neared.

Then it was Boston’s turn. The Celtics were a little slow about it, but over the first eight-plus minutes of the fourth quarter, they outscored Philadelphia 15-4, edging ahead 98-96. They got the lead to five with two minutes left but couldn’t hang on, Harden’s floater tying it at 107 and Marcus Smart missing a 3 at the buzzer for OT.

Those five extra minutes thrilled and tormented both sides. A long Sixers possession with two resets finally ended with an Embiid turnaround jumper to get them within 112-111. Tyrese Maxey grabbed Smart on a rebound opportunity, only to have Smart then turn over the ball. Embiid knocked Smart down for a charge, a call Rivers unsuccessfully challenged. Boston’s Al Horford had a 3-pointer rim out, then got whistled for back-to-back fouls six seconds apart.

By that point, deep reserves on either team could have gnawed their fingernails down to the first knuckle.

With 38 seconds left in OT, Celtics forward Jayson Tatum pushed Maxey with his off-arm, a pretty clear — but missed — push-off on his way to a step-back 3. Celtics 115, Sixers 113. Until Philadelphia fed Embiid in the middle against Tatum and Brown, seeing that mismatched, cheated in from his denial position on Harden in the right corner. Oh, did “The Beard” make him pay for that.

“A gamble at the wrong time,” Brown called it. “A bad read.” Embiid might have forced a second overtime, but Harden sent everybody on to Boston with the 24-footer. And even then, Smart’s attempted three at the end of a too-leisurely last trip upcourt, which would have flipped the outcome to 118-116, came a tick too late.

None of it recommended for the faint of heart.

3. Embiid gave the Celtics their opening

Not many would quibble with the Philadelphia center’s final stats line: 34 points, 13 rebounds, one steal and 12 of 15 shooting from the foul line. But he spotted Boston 12 minutes with a dismal fourth quarter in which he let himself be guarded and looked hesitant to force action inside several times.

Horford is an underrated and versatile defender, but he is physically dwarfed by Embiid’s massive presence. Didn’t matter in the fourth, though, as the Boston not-as-big man stayed in front of Embiid, turning him into a ready passer as the Sixers’ offense bogged down.

Embiid made only one of his six shots in that quarter and his team shot 6-for-19, getting outscored 24-15. He showed such little inclination to attack Horford, you wonder if Brown would have felt the need to double off Harden on that game-winner had Tatum not switched onto the Philadelphia center.

Collectively, the Sixers ran out of gas for much of the fourth. But Embiid was not as forceful in that period as he had been earlier, and teammate P.J. Tucker called him on it.

“Nobody can guard Joel one-on-one,” Tucker said. “I’m sorry, there’s no disrespect to Al [Horford] or anybody else. I’ve guarded him for a lot of years, and when he’s aggressive and assertive, it’s impossible. I saw him two or three plays in a row not [play like] that, and we can’t have that. Not with the season on the line.”

Embiid knew, to the point of overstating things by the end.

“I was terrible,” he said. “I got to be better and I will be better.”

4. Tatum showed his resiliency

It was largely due to Tatum’s ability to bounce back from a disappointing first half that Boston was able to come so far back. Plenty of players, especially shooters, would have dragged his frustrating first half — 1-for-9, two points, two fouls — right across the intermission and made it a forgettable night overall.

Instead, the 25-year-old continued to demonstrate his growth by leaving the bad stuff right where it happened. He scored 17 points in the second half, hitting six of his eight shots, added another nine rebounds and dished four assists. The Celtics, rather than getting outscored by nine this time, bested the Sixers by that same amount. And in overtime, Philadelphia scored nine, Tatum scored five and Smart chipped in three.

His final results looked pretty good — 24 points, 18 rebounds, six assists, a steal and four blocks — and Tatum was candid in evaluating his night.

“I get paid a lot of money,” he said. “I do it all: blocks, rebounds, steals. Points are what you expect but you know, I take pride in impacting the game in every way possible.”

5. The ballad of P.J. Tucker plays on

Just when it seems as if Tucker should be paying for a ticket, he does something to remind even casual fans why so many NBA teams value his brand of toughness, defense and Mixmaster presence in games that matter most.

Through the first three games, the burly 38-year-old had scored 14 points with 10 rebounds, logging a cumulative minus-24 in his 82 minutes. Meh at best, right? Ready for a Udonis Haslem emeritus role, maybe.

Tucker’s raw numbers weren’t much in Game 4 either: six points, three rebounds in more than 31 minutes. But he had much to do with Tatum’s cockeyed shooting start. And with the Sixers down 105-102 with barely a minute left, it was Tucker who grabbed Tobias Harris’ air ball, laid it up and got fouled for the 3-point play to tie.

(Okay, so Tucker also was the culprit in knocking down Smart for a foul on the ensuring possession, but we’re laying out “the legend of…” stuff here.)

“The three-point play is just will, determination and wanting to win,” Tucker said. “I just got back in the game, so I had to leave an imprint somehow.”

Tucker has played for six different NBA franchises, but has left a long line of appreciative coaches in his wake. Milwaukee won its championship with him two years ago and has missed him ever since, trying in vain to cast Jae Crowder as a replacement. Miami was happy to swipe him from the Bucks, less happy when he joined his old pal Harden in Philadelphia.

Now he’s working his gritty magic for the Sixers, so stop counting his stats already.

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Steve Aschburner has written about the NBA since 1980. You can e-mail him here, find his archive here and follow him on Twitter.

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