BOSTON — Few people could have imagined the Boston Celtics would lose their second-best player five minutes into the season and their best player in March and still reach the Eastern Conference finals.

But fortunately for the Celtics, the future is now, thanks to the improvement and poise of rookie forward Jayson Tatum and second-year forward Jaylen Brown. Tatum (25 points) and Brown (24 points) led the C’s in scoring as Boston eliminated the Philadelphia 76ers in Game 5 of its second-round NBA playoff series Wednesday night.

“It’s a sight to see,” Celtics guard Marcus Smart said of Tatum and Brown’s clutch performances to close out the series. “Those guys have been thrown in the fire early and they’ve responded very well, and exceeded, probably, expectations that guys had for this team. They’re going to keep getting better.”

Boston’s young duo combined to shoot 18-for-28 from the floor (3-for-4 on 3-pointers), and Tatum scored a huge bucket to put the C’s up 111-109 with 22.5 seconds remaining.

Tatum now has scored 20 or more points in seven straight playoff games, the most ever by a Celtics rookie and the most ever by a player 20 years old or younger. Brown now has scored 20-plus four times in this postseason, and he looks fully healthy after being limited earlier in the series because of a right hamstring injury suffered in the first round.

The Celtics will need Tatum and Brown to consistently score 20-plus against LeBron James and the Cleveland Cavaliers in the Eastern Conference finals, which begins Sunday in Boston. James arguably is playing the best basketball of his storied career, and the C’s can’t afford rookie mistakes from Tatum and Brown if they’re going to dethrone the reigning conference champs.

Tatum and Brown, to their credit, have shown they’re up for any challenge through the first two rounds.

Here are some other notes from Celtics-Sixers Game 5:

— Here’s another note about Tatum.

— One Celtic who must dramatically improve in the conference finals is Marcus Morris. The veteran forward has provided consistent scoring off the bench all season, but he did not shoot well against the 76ers. He scored just six points on 1-for-10 shooting in Game 5 and shot just 30.8 percent (31.8 percent from beyond the arc) in Round 2. Those numbers were well below his regular-season percentages (43 percent from the floor and 36.8 on threes).

— 76ers center Joel Embiid played a fantastic Game 5 and tied Dario Saric for the team lead with 27 points. He also shot 9-for-11 from the foul line and grabbed a game-high 12 rebounds.

Embiid couldn’t tie the score on the 76ers’ second-to-last possession, though. He wasn’t able to make a shot from in close over Celtics center Aron Baynes and lost the ball out of bounds before putting up a second shot.

Success in the clutch has eluded Embiid early in his career.

— The first half was pretty even, with no team building a lead larger than five points until the C’s closed the second quarter on an 11-2 run (including eight points in the last 56 seconds of the half), capped by a buzzer-beating 3-pointer from Terry Rozier. That shot put the Celtics up 61-52 at halftime.

The 76ers shot 54.8 percent from the field in the first half, but they still trailed by nine because of eight turnovers and only two made 3-pointers.

— Home court advantage in the playoffs is very important in the NBA, and one example of why is Boston’s record in Game 5s at TD Garden.

— Baynes played his role as well as he could’ve hoped in Round 2. He scored 13 points with a team-high nine rebounds and five steals in Game 5. He also continued to hit from beyond the arc.

Baynes also played solid low-post defense on Embiid, got Embiid to shove him for a technical foul and he even showed off some impressive low-post moves.

Baynes didn’t completely slow down Embiid in this series, but he held his own against the 76ers center 1-on-1 in the low post, and that allowed the Celtics to not have to double team Embiid and leave shooters open on the perimeter.

Here’s the stop Baynes made on Embiid with the Celtics up two in the final minute:

And here’s what Baynes said about that possession.

“He’s so talented offensively and he’s such a great player that you just try to make it as tough as you can every time,” Baynes said. “I knew he was going to make it physical and try to draw a foul if nothing else. I was just trying to play him as straight up as I could and try to put him at a less than optimal angle. I gave him his left hand. Like I said, five guys making plays, and Terry came in and made a big play for me as well.”

— Saric gave another good performance for the 76ers. He scored 27 points on 6-for-12 shooting (2-for-2 from 3-point land). He also went to the free throw line 11 times and made eight of his attempts. Saric added 10 rebounds, four assists and one steal as well.

— The Celtics were plus-6 in the turnover battle, and Rozier was a huge part of that. The third-year point guard is averaging just 1.3 turnovers per game in the playoffs.

— The Celtics made a bit of history with their conference final berth, one that shows the resiliency and heart of the team.

Thumbnail photo via Greg M. Cooper/USA TODAY Sports