LeBron James stared up at the scoreboard in Bankers Life Fieldhouse, at a 25-point deficit, before retreating with his teammates to the locker room. The likelihood of the Cavaliers winning Game 3 of their first-round series against the Pacers was small — 1.2 percent, according to ESPN Stats and Information.

Behind a turbocharged James, the Cavaliers mounted the largest halftime comeback in NBA postseason history, winning 119-114. The 32-year-old poured in a 41-point triple-double, scoring 28 second-half points. He either scored or assisted on 73 points, the highest single-game total of his playoff career, which consists of 203 games.

In total, LeBron finished the opening round with robust averages of 32.8 points, 9 assists, 9.8 rebounds and two blocks per contest. If that assist total seems high, it’s because it’s the most he’s ever averaged in an opening round playoff series. His averages in points and blocks are the second highest of his first-round playoff career, his average in rebounds the third highest.

Considering his age, workload, production and efficiency, it was arguably the most impressive first-round series of LeBron’s career.

So, why didn’t the Cavaliers blast the Pacers into oblivion in Round 1? Why was every game a slog? Simple: Cleveland’s defense has been terrible.

As The Washington Post’s Neil Greenberg noted, the Cavaliers entered the postseason allowing 108 points per 100 possessions, the worst defensive rating of any LeBron-led team. It only got worse, with the Cavaliers allowing 111 to Indiana, a squarely middle-of-the-pack offensive unit.

According to defensive efficiency, it was the third worst playoff series of LeBron’s career.

The Cavaliers allowed one point per possession in the opening round, according to data provided by Synergy Sports, which ranks ninth among playoff teams. Just one team this postseason is allowing more points per possession to ballhandlers in pick-and-roll situations (1.075), continuing a trend that has plagued the Cavaliers all season. This is largely because Cleveland has no true rim protector and Kyrie Irving is one of the worst pick-and-roll defenders in the league, allowing 0.956 points per possession during the regular season and ranking in the 19th percentile among primary pick-and-roll defenders. He was — somehow — even worse in the opening round, surrendering 1.188 points per possession and ranking in the 12th percentile. Indiana point guard Jeff Teague easily and repeatedly gashed Irving’s high-screen-and-roll defensive coverage, easing into midrange jumpers and finding running mates racing toward the rim.

This is worrisome for Cleveland moving forward, considering Toronto, a team that led the entire league in points scored by pick-and-roll ballhandlers, potentially awaits in the second round.

In its opening series, Cleveland found success double-teaming ballhandlers during pick-and-roll possessions, but the team might want to tailor that approach, considering the Raptors are scoring 0.812 points per possession when the defense traps, the second highest scoring rate of any postseason team.

Worth noting is, outside of Cleveland, Toronto is the deepest, most experienced remaining team in the Eastern Conference.

Additionally, while Cleveland was a top-half defense against jump shots throughout the regular season, only two teams this postseason are allowing more points per possession than the Cavaliers on those looks (1.04). Indiana was gift-wrapped 15.5 field goal attempts per contest where the primary defender was more than 6 feet away from the shooter — shots that NBA.com defines as wide open.

These defensive deficiencies are partially why in Game 3, LeBron played the final 14 minutes, 29 seconds without the help of Kyrie Irving and Kevin Love. Despite the two all-stars riding the pine, Cleveland outscored Indiana by 18 in the game. Asking LeBron to shoulder the load on both ends of the floor — he leads all postseason players in minutes, has the second highest playoff usage rate and is defending 11.5 shots per game, the highest mark of any Cavalier — could produce a breaking point.

Irving and Love’s shortages weren’t exclusive to the defensive side of the floor, either. Both players’ averages in efficiency dropped in the opening round relative to the regular season. Irving’s true-shooting percentage spiked to 58 during the regular season, 0.3 percentage points shy of a career high. However, it dropped to 50 in the opening round, and he shot a putrid 21.9 percent from beyond the arc. Love, whose per-game scoring output dropped from 19 to 15.5, slashed his turnovers during the regular season to produce a turnover rate of 10.9 percent, right around his career average. In the opening round of the series, it spiked to 16.5 percent.

The addition of ball-hawking defenders like P.J. Tucker and Serge Ibaka has only bolstered the Raptors’ ability to smother opponents. Toronto generates 17.4 percent of its total points by forcing turnovers, a percentage that leads all active postseason teams. Dwane Casey’s club ranks no lower than third in points allowed per possession this postseason in overall defense, half-court defense, pick-and-roll ballhandler defense and isolation defense. In short, it won’t be any easier for Irving and Love to find a rhythm in the second round.

Defensively, it’ll be difficult for LeBron to continue carrying the burden of Irving, who ranks in the 10th percentile this postseason in overall defense as defined by points allowed per possession (1.25). Deron Williams, however, has been a serviceable backup, playing well in his place. Love has had his struggles, but still ranks in the top-half percentile of all postseason players in post-up and spot-up defense.

Cleveland’s eyes remain on another championship, but the defense must improve as the postseason progresses. This team might not be able to withstand another defensive performance like what unfolded in the opening round, considering that among the remaining Eastern Conference teams, Toronto, Washington, Milwaukee and Boston all ranked in the top 13 in offensive efficiency. As it often goes, though, much will depend on how far LeBron can carry this roster.