The Boston Celtics and Milwaukee Bucks have faced off in plenty of playoff showdowns over the years, including four clashes in the 1980s alone, during the heyday of Larry Legend and Sid the Squid. This year’s series renewed the rivalry after a 31-year hiatus, and it’s largely lived up to expectations so far: Game 1 featured a pair of buzzer-beaters at the close of regulation before Boston won in overtime, then the Celtics handily took Game 2. But the Bucks managed to claw their way back, running away with Game 3 before winning Game 4 in thrilling fashion to tie the series up.Here are four questions to ponder as the teams head back to Boston and begin what’s now a best-of-three affair.Can Milwaukee’s offense stay hot?The biggest statistical trend helping to turn the tide in this series has been the newfound efficiency of the Milwaukee offense, which went from averaging a mediocre 105.9 points per 100 possessions1The league’s regular-season average was 106.2. in Games 1 and 2 to a scorching 122.8 points per 100 in Games 3 and 4, according to NBA Advanced Stats.You don’t heat up an offense that quickly without an abrupt change in shooting fortunes, and the Bucks have certainly turned things around from beyond the arc. In Games 1 and 2, Milwaukee averaged just 7.5 3-pointers per game — a number below its paltry regular-season average of 8.8 — with only Khris Middleton (who, granted, made a whopping 4.5 threes per game) providing any consistent spacing from the outside. Over the past two games, however, Milwaukee has increased its threes per game to 13, with 10 different players making at least one 3-pointer. In Game 3 alone, the Bucks set a franchise postseason record with 16 threes, according to ESPN’s Stats & Information Group.So much of the Bucks’ offense is tied up in the playing style of its leading talent, Giannis Antetokounmpo, a player whose unmatched combination of size, length and athleticism allows him to get shots as close to the basket as he wants. (During the regular season, Giannis led the NBA in paint scoring at 15.7 points per game, and the Bucks were tied for the fifth-most buckets from the restricted area.) But as great as Antetokounmpo is, the reality of the modern NBA is that such a defense-collapsing force needs to be complemented with shooting that pushes opponents into impossible defensive dilemmas.The Bucks have often struggled to pose such a threat from deep; they made the league’s fourth-fewest threes per game during the regular season. But they hinted at a fuller offensive potential over the past few games versus Boston, with their increased focus on long-range shooting. It’s worth watching to see if Milwaukee can keep pairing those threes with a Giannis-led interior attack to potentially key a playoff series victory.Can Boston get Terry Rozier back on track?One of the keys to whether Boston could survive the loss of Kyrie Irving has been the play of Terry Rozier, the third-year guard who enjoyed a breakout regular season and took on an increased role in March after Irving’s knee surgery. Rozier was stellar in the first two games of this series, averaging 23 points (on 46.9 percent shooting) and zero turnovers per game as the Celtics built their 2-0 lead. But he has cooled down substantially, with his averages falling to 9.5 points (on 26.3 percent shooting) and 3 turnovers per game in Boston’s pair of losses.Which Rozier will show up now? It will depends on how he cracks the defense of Eric Bledsoe and, increasingly, Matthew Dellavedova — who guarded Rozier with success in Games 3 and 4. That pair has succeeded in making Rozier much less dynamic as both a passer and a scorer in the past two games, holding him to 8.5 potential assists per game (down from 10 in Games 1 and 2) and a usage rate of 18.4 percent (down from 20 percent).The Celtics have still gotten plenty of scoring punch from Jayson Tatum and Jaylen Brown, who in Game 4 became the second pair of teammates under 22 years old to ever notch 55 combined points in a playoff game, according to the Elias Sports Bureau — joining Russell Westbrook and Kevin Durant from 2010. But with Rozier suddenly struggling, the Celtics are missing an important version of the stellar backcourt production that had been so central to the team’s success, both with and without Irving.Will Giannis’s teammates keep up the help?As noted, Milwaukee’s chances are inextricably tied to the Greek Freak — and Antetokounmpo has been holding up his end, delivering a superstar performance. Over the past two games, he’s anchored the Bucks with a 30.1 percent usage rate, 64.5 true shooting percentage and 28.9 assist percentage as the team was fighting its way back to draw the series even. But the irony is that those numbers weren’t too different when Milwaukee was falling into its early series hole: In Games 1 and 2, Antetokounmpo had a 30.2 percent usage rate, a 66.3 true shooting percentage and a 28.8 assist percentage.So for the Bucks, the determining factor isn’t merely how well Giannis plays — it’s how much everyone around him contributes. In the two opening losses, Antetokounmpo’s teammates averaged 74 total points and 13 total assists per game, with a 57.3 percent true shooting mark. In the Bucks’ two victories, those numbers skyrocketed to 87 points, 20.5 assists and a 65.2 true shooting percentage.Of particular note has been the strong play of Middleton and an expanded role for Jabari Parker, who was limited to about 12 minutes per game in Games 1 and 2. Parker has come on strong since, averaging 16.5 points (on 54.5 percent shooting), 6.0 rebounds, 2.5 blocks, 1.5 steals and only 0.5 turnovers per game in Games 3 and 4. He helped Milwaukee’s bench outscore Boston’s 31-15 in Game 4, an important edge in a matchup decided by just two points.This doesn’t mean Giannis should be taken for granted, of course. He’s personally dominating this series, with his own play putting teammates in a position to produce efficient numbers for themselves. He willed the Bucks to victory in Game 4’s closing seconds, fighting off Tatum under the rim to tip home the game-winning bucket with 5.1 ticks to go. But the biggest difference between Milwaukee’s losses and wins in this series has been how well the Bucks not named “Antetokounmpo” have been able to execute in their supporting roles.Where’s Al Horford?Though Irving was forced to shoulder Boston’s scoring attack after Gordon Hayward went down with injury five minutes into the season, the 2017-18 Celtics’ most valuable player might have been center Al Horford, whose mega-efficient combination of skills make him the unsung catalyst who improves everyone around him.Boston’s first two games against Milwaukee featured Horford at his versatile best. He scored 20 points per game — while needing only 9.5 shots per game to do it — grabbed 8.5 rebounds and dealt out 4 assists. Every time you looked, he was doing some kind of proverbial “little thing,” like setting a key screen, contesting a shot or getting to the line. Despite taking responsibility for only 15.2 percent of Boston’s offensive attempts2Including shots and turnovers. while in the game, Horford managed to personally account for 17.8 percent of all the positive actions that took place on the court (for either team), according to NBA Advanced Stats.Horford didn’t play poorly in the following two games. He still averaged double-digit points and shot better than 50 percent from the floor. But he individually accounted for only 11 percent of the positive events that happened when he was on the floor, and the Celtics went from plus-4.9 points per 100 possessions with him to minus-8.9. On defense in particular, he had few answers for Antetokounmpo’s forays to the basket (in fairness, who does?), as the Bucks’ offensive rating swelled to 119.9 with Horford on the court.One of Horford’s greatest gifts is that he doesn’t need plays called for him to make a big impact. But there’s a fine line between unselfishly playing all-around basketball and not being involved enough, and Horford was probably on the wrong side of that line as Milwaukee chipped away at Boston’s 2-0 lead — especially in Game 4. He’ll need to get back to exerting his influence at both ends of the court in Game 5 for the Celtics to turn this series around.Check out our latest NBA predictions.