The Miami Heat have been completely outplayed so far in the first round of their NBA Playoffs series against the Milwaukee Bucks. They lost the first three games of the matchup and now find themselves on the verge of being swept by the Bucks, who are looking to exact revenge for last season's 4-1 drubbing.Why have the Miami Heat struggled against the Milwaukee Bucks in the 2021 NBA Playoffs?The Miami Heat finished their regular season in sixth place, after navigating through multiple bouts of COVID-19 cases. This led to a re-match of last season's Eastern Conference semi-finals, which the Heat had won comfortably. However, the script has completely flipped this year, as Erik Spoelstra's men will take to the court on Saturday looking to avoid the embarrassment of a sweep.Here are three reasons why Jimmy Butler and co. have struggled to get going against the Bucks.#3 Jimmy Butler's poor formJimmy Butler has been poor for the Miami Heat in the 2021 NBA PlayoffsJimmy Butler forced overtime in Game 1 of the matchup, breezing past Giannis Antetokounmpo for a two-point shot in the dying moments of regulation. He still didn't have a great overall game, shooting 4-22 from the field. Fans and neutrals expected a player of Butler's caliber to respond with a vintage performance, but things have arguably become worse since then.Jrue Holiday is +88 in this series, the highest on the Bucks by far.Jimmy Butler is -68 in this series, the lowest on the Heat by far. pic.twitter.com/eLBp0oGQBa— StatMuse (@statmuse) May 28, 2021Butler finished Game 2 with 10 points on 4-10 shooting, while Game 3 saw him post a stat line of 19 points, 8 rebounds and 6 assists. He still finished the third game with 7-17 shooting and a team worse -26. Butler is the heart and soul of the Miami Heat and personifies 'Heat Culture', but his failure to click has been one of the major reasons behind their struggles against the Milwaukee Bucks.Also Read: Who has the most steals in NBA history?#2 Mike Budenholzer's key adjustmentGiannis Antetokounmpo of the Milwaukee Bucks finishes at the rim against the Miami HeatGiannis Antetokounmpo had a torrid playoff series against the Miami Heat in 2020, as the 'Greek Freak' couldn't exert his dominance against the 'defensive wall' setup by Erik Spoelstra. He had to settle for jump shots instead of his customary forays into the paint, which eventually led to the Milwaukee Bucks struggling offensively throughout the series.BUCKS ARE CLOBBERING THE HEAT 😳 One game away from sweeping Miami 👀 pic.twitter.com/6XMBNUJ5iV— ESPN (@espn) May 28, 2021Mike Budenholzer has countered that by using Giannis Antetokounmpo in pick-and-roll action, with Khris Middleton and Jrue Holiday being used as ball-handlers. The Miami Heat haven't been able to counter that adjustment, and Middleton and Holiday's shooting and playmaking abilities have ensured the Milwaukee Bucks 'Big-3' are able to execute their roles perfectly.#3 Miami Heat have been completely trounced on the boardsBobby Portis of the Milwaukee Bucks goes up against Tyler Herro of the Miami HeatRebounding was a major issue for the Miami Heat during the regular season, as the team finished second-last in the NBA in rebounds per game. They averaged a poor 41.5 rebounds per game, allowing teams to dominate them on the offensive glass (league-worst 8 rebounds per contest).Meanwhile, the Milwaukee Bucks ended the regular season as the second-best overall and best defensive rebounding team in the league. Their success on the glass at both ends of the floor has persisted in the playoffs as well, as they have out-rebounded the Heat in all three games.If the Miami Heat don't show more pro-activeness on the boards in Game 4, it could be the last game of their campaign for them.Also Read: 5 times Russell Westbrook clashed with fans during NBA games