Ten games into the season and the Boston Celtics were a train wreck. 

The 4-6 start felt like just the beginning. In their home opener against Toronto, Boston was drilled 115-83, the first of several early home games that brought out the boo-birds. 

Now, it's clear those tough-to-swallow losses hardened this Celtics team in ways that few, perhaps besides head coach Ime Udoka, would have envisioned. Now they are four wins away from a trip to the NBA Finals. 

The Celtics eliminated the defending NBA champion Milwaukee Bucks on Sunday, advancing to the Eastern Conference Finals where they will face the Miami Heat in Game 1 on Tuesday, a rematch of the 2020 Eastern Conference Finals. 

For Boston, this has been a gravel-paved season. Their slow start begat trade rumors. Injuries to multiple starters—Jaylen Brown, Marcus Smart and more recently, Robert Williams III—hurt continuity. Trust issues with key players forced uncomfortable public drama. The roster begged for questions, with uncertain answers:

—Can Jayson Tatum and Jaylen Brown become the leaders Boston is looking for?

—What contributions will come from a young, inexperienced bench in uncomfortable environments? 

—Will Robert Williams III stay healthy enough to contribute significantly this season? 

—Is Ime Udoka the right hire to replace Brad Stevens as the Celtics' head coach? 

But you could have asked those same questions leading into the matchup with Milwaukee. Note some of the more notable challenges the Celtics encountered—all overcome vs. the Bucks: 

Handling the absence of starting center Robert Williams III (knee), a key to their top-rated defense, for the last four games.

Withstanding two-time league MVP Giannis Antetokounmpo, who delivered one of the most statistically impressive playoff series performances ever, becoming the first player in NBA history to earn at least 200 points, 100 rebounds and 50 assists in the same playoff series.

Winning a pair of road games against the Bucks, one of the league's top home teams this past season.  

A rookie coach vs. a proven championship coach. 

Nothing has been given to these Celtics, a theme that goes back to their first turning point.