PHILADELPHIA -- The message came to T.J. McConnell from assistant coach Lloyd Pierce just before the team held Monday's 2 p.m. walk-through at Wells Fargo Arena. With the 76ers facing a 3-0 series deficit to the Boston Celtics, Philadelphia coach Brett Brown had consulted with the staff and decided to replace struggling forward Robert Covington in the starting lineup with McConnell.

Pierce told McConnell the team cared about only three things -- energy, spirit and covering Celtics guard Terry Rozier.

"You need to come in with a spirit," Brown said. "You need to come in with a tenacity. T.J. epitomizes that, so we start him. To declare that to a team -- and you're fighting for your life -- and to then put him in an environment that lets him do it makes more sense to me as a coach. You can't do it a lot, but to put him in an aggressive mindset in an aggressive defensive format, and to deliver the message that I've just said, it equals something."

That something was a 103-92 Philadelphia win in Game 4, extending the Eastern Conference semifinals to a fifth game in Boston on Wednesday.

To stave off elimination Monday night, the Sixers had a lengthy to-do list against a disciplined Boston team that had gummed up one of the league's fastest attacks, stretched one of the league's most aggressive defenses and disheartened one of the league's most exuberant young rosters -- one that had entered the playoffs riding a 16-game winning streak and waxed the Miami Heat 4-1 in the first round.

Enter McConnell, a logical candidate to address each of these items. A skilled ball handler, the guard helped decongest a Philadelphia half-court game that had departed so far from its motion and pass-happy rhythm that it was barely recognizable. In the 39 possessions that McConnell brought the ball up the floor on Monday night, the Sixers generated a fat 1.23 points per possession, according to data collected by Second Spectrum.

"He changed everything," 76ers center Joel Embiid said. "He was pressing full court the whole time doing his job, running the offense, getting guys involved, making shots, layups."

Under McConnell's direction, the Sixers achieved some of their zippiest half-court action in the series. It was less the graceful choreography of the second half of the regular season and more guerrilla theater, but only two of those 39 possessions resulted in isolation plays.

McConnell also generated plenty of production in his own right -- 19 points on 9-for-12 shooting from the field, seven rebounds and five assists. Incredibly, he scored 14 points in the paint in Game 4 -- the most for any player in the game -- and converted six of his seven shot attempts in the restricted area, according to ESPN Stats & Information research.

"All guards try to drive downhill, and it opened the space for T.J.," 76ers forward Dario Saric said. "And T.J. just took it."

The 76ers are plus-38 with T.J. McConnell on the court in the series, the highest plus-minus of any Sixers player. Bill Streicher/USA TODAY Sports

Saric had a breakout game of his own, scoring a game-high 25 points (9-for-17 from the floor, 6-for-6 from the line). He was opportunistic, putting the ball on the floor and driving against smaller defenders and shooting without hesitation facing up.

The downstream effect of McConnell's presence offensively revealed itself in positive ways. Embiid, who was inefficient in his 15 direct post-ups in Game 3, had only three direct post-ups on Monday, when he was recast as an effective roll man, dancing with both McConnell and Ben Simmons. For the Sixers, another ball handler in McConnell created another bully in Simmons. Witness the familiar two-man action the Sixers ran for Embiid with JJ Redick late in the game on one of those McConnell-initiated possessions -- but with Simmons diving low to collect the pass from Redick for the dunk inside.

With McConnell as the primary matchup on Rozier, the Celtics' point guard endured his least productive outing of the series, held to 11 points on 4-for-11 shooting from the field and only a pair of assists. McConnell is a notorious pest who routinely picks up opposing ball handlers from 94 feet out, and Rozier was spared none of it.

In an effort to intensify their overall effort on Monday, the Sixers sent regular blitzes and double-teams at the Celtics. Yet despite leveraging themselves on the perimeter, the Sixers also were able to keep Embiid and the rest of the backside of their defense on short rotations, avoiding the mishaps that plagued them in Game 3. Such is the consequence when formerly easy swing passes and reversals meet pressure.

Tactical considerations aside, McConnell's imperative in Game 4 was largely spiritual. In many respects, McConnell personifies the humble origins of this 76ers team, one that compiled a 10-72 record during his rookie campaign in 2015-16. That season, Brown would tell his beleaguered squad after a bad loss that he needed to improve his coaching in order to put the team in a better position to succeed. And it was McConnell who told his coach he wouldn't hear any more of it: "You're coaching your ass off," McConnell told him, adding that the losses were more a product of personnel than preparation. "This isn't on you."

Like Brown, McConnell is an eternal optimist, befitting of his pedigree as a guy NBA scouts regarded as ill-suited for the world's most competitive league. Accordingly, the ovations for McConnell from the home crowd each time he checked out of Game 4 were rousing, particularly in the third quarter, when he scored or assisted on 16 points.

"It was a pretty special moment," McConnell said. "I think we have the best fans in the NBA. They've been here through the dark times, and they've certainly been here on our rise."

Who can blame them? They were stranded on a shipwrecked island with the guy for three years, finding shelter in sea caves, catching fish with spears, using coconut husks for rope. And on a night that might be their final glimpse of the 2017-18 team that has started to deliver on its promises, McConnell orchestrated the rescue.