For the third time in four seasons, the Boston Celtics are squaring off with the Miami Heat in the Eastern Conference Finals.

While the matchup is the same, the seeding is very different. The Heat were the top seed last year but now find themselves as an eighth seed. And even though the C's are the second seed with home-court advantage, they should not make the mistake of underestimating a tough Miami team.

Led by star forward Jimmy Butler, the Heat had to pull off some major upsets this postseason to get back to where they were last year. The Celtics have been tested too, as they're fresh off a seven-game series against 2023 MVP Joel Embiid and the Philadelphia 76ers.

In order to reach their second-straight Conference Finals, Boston's stars had to propel them past Philly. Four-time All-Star Jayson Tatum erupted for 51 points in Game 7 and two-time All-Star Jaylen Brown added an efficient 25 points. Against Miami, the Celtics will need their best players to perform once again.

But outside of Tatum and Brown, who will step up? Guard Derrick White was the X-factor in the first round, yet he didn't look great versus Philadelphia. To beat the Heat the C's will have to get contributions from more than just their stars, so who's up to the task?

Celtics' X-factor vs. Heat: Robert Williams III

Before the Celtics inserted center Robert Williams III into their starting lineup last series, they were down 3-2 against the Sixers.

Once he saw a minutes increase and joined the starting five, Boston won two straight and completed the comeback. This isn't to say that Williams is the reason why the C's advanced to the Conference Finals, yet he was certainly a factor.

During the 2022-23 playoffs, the big man is averaging 6.7 points, 6.4 rebounds, and 1.3 blocks in just 21.9 minutes per outing. While these statistics won't jump out at you, Williams' numbers in the games he started are particularly impressive.

In Game 6 versus Philadelphia, the 6-foot-9 center posted 10 points, nine rebounds, and two blocks in 28 minutes. He also had a game-high plus-minus rating of plus-18. Then in Game 7, he put up six points, five rebounds, and one steal in 30 minutes of play.

Williams' defense was critical in the Eastern Conference Semifinals, and even Embiid himself said the “Time Lord” made a huge difference on the floor:

Although he isn't a shooting threat, Williams has enough of an impact on defense to make him deserving of more playing time. And while injuries have hindered him throughout his career, Williams has been durable this postseason and has yet to miss a game.

In last year's Eastern Conference Finals, “Time Lord” wasn't as healthy. He missed Game 3, which Boston lost 106-98, due to a troubling knee issue. Despite the injury bug, he averaged 9.2 rebounds, six points, and two blocks in that series against the Heat. If Williams can have a similar performance this year, Boston will be in a good spot.

Even though Miami's best player this postseason is undoubtedly Butler, center Bam Adebayo is a significant threat. The two-time All-Star is averaging 18.1 points per outing, and he's notably averaged 25 points per game against Boston this season. The Celtics could play some more small ball versus the Heat, however, Williams will likely be paired up with Adebayo more often than not.

Williams' defense on Adebayo will be pivotal to Boston's success. Butler will get his buckets at times no matter what the C's might throw at him, so they'll have to work hard to limit his teammates. Adebayo is the next option on the Heat, meaning Williams must slow him down in the paint to curb the Heat's offense.

Overall, the Celtics are in for another challenge with the Miami Heat. The Heat have shooters, a clutch star, and a solid co-star who's matchup up well with the C's in the past. In order to return to the Finals, the Celtics have to be ready for an all-out war with a gritty, experienced Miami team.