BOSTON (CBS) — Thursday probably wasn’t a great day for the Boston Celtics. They had to relive their Game 5 collapse from Wednesday night and then head to Milwaukee for Friday night’s must-win Game 6 against the Bucks.

It must have been an interesting film session by Ime Udoka, who had no shortage of issues to highlight from his team’s avoidable crumble in Game 5. To the Celtics’ credit, they were all ready to move on after the events of Wednesday night played out, and all of them were confident that those mistakes would not be repeated Friday night.

READ MORE: Tatum, Brown shoulder blame for Celtics' third quarter collapse in Game 1

As just about everyone put it after Wednesday’s loss, the series is not over. The Celtics have already won a game in Milwaukee, and probably should have won two. (Again, more of their own undoing.)

But they know that they missed a golden opportunity and made things extremely difficult on themselves. Their backs are against the wall and they now have to win two straight against the defending champs, starting with Friday night in the Bucks’ house. Here’s how the Celtics can force a Game 7 back at TD Garden on Sunday afternoon.

Tatum Needs To Be Tatum

We’ve written this before, and we’re writing this again. Looking at Boston’s losses in Game 3 and Game 5, the common denominator is that Jayson Tatum was not that good in either of them.

Sure, he had 34 points on Wednesday, but he hit just 12 of his 29 shots. He was an abysmal 2-for-11 from three-point range. And when it mattered the most in crunch time, Tatum did… nothing. He didn’t score for the final 3:30 of the game and took just two shots over that span. He was late to move on Boston’s second-to-last possession (though Al Horford was late to set a screen as well), leaving Marcus Smart to take the ball and go for a layup. It was called a miscommunication after the game, which is inexcusable with the game on the line. That’s something the Celtics of the first half of the season did, not the Celtics that have essentially dominated since early January.

The Bucks aren’t making things easy on Tatum this series. But with his star status comes the expectation that he is going to lead the team each and every night. We’re still waiting for a “Jayson Tatum Game” this series, and Game 6 would be a fantastic time for him to really break out. Otherwise, he may not get another opportunity.

Box Out, Please

Seventeen offensive rebounds. If you started shaking after reading that phrase yet again, we apologize.

“If we box out, we win that game,” Marcus Smart said after Game 5. It really was that simple.

And it wasn’t just Bobby Portis’ offensive board off Giannis Antetokounmpo’s miss free throw, though that is totally inexcusable with a game on the line. Again, the Celtics gave up 17 offensive rebounds on Wednesday.

The Celtics have been out-rebounded on the offensive glass in the last three games by a 43-20 margin. The Celtics won that battle in Game 2, 7-5, and both teams pulled down 10 offensive boards in Game 1. But with all of those extra looks, Milwaukee has a 71-51 edge over Boston in second-chance points this series.

READ MORE: Dreadful third quarter dooms Celtics as Butler leads Heat to 118-107 victory in Game 1

Boston relying on small lineups, plus the absence of Robert Williams, certainly play into Milwaukee’s dominance on the offensive class. But the Celtics need to stop giving the Bucks so many extra chances if they want to force a Game 7.

Stop Complaining

Yeah, something else we’ve heard over and over and over again this postseason. But the Celtics really need to cut it out when it comes to complaining to the officials. There have been far too many occasions where someone hasn’t gotten back on defense because they’ve been too busy throwing their arms up and giving a stare to a ref who didn’t blow their whistle, leaving the defense shorthanded as the Bucks raced out in transition.

The Bucks hit a trio of transition threes (and four overall) during their comeback in Game 5 because someone on the Celtics was barking at a ref. Tatum was guilty twice. Jaylen Brown and Grant Williams each had one of those instances. Because those guys weren’t defending, the Bucks were able to find open looks and knock them down.

Seriously, Celtics, knock it off. It’s a terrible look and it’s really hurting the team.

Keep Pushing

Following a pretty dramatic comeback win in Game 4, Boston took its proverbial foot off the gas to close out Game 5 and it cost them dearly. The Celtics got complacent on offense and settling for long pull-ups instead of attacking the rim, and they got extremely stagnant on defense.

The Bucks outscored the Celtics 23-9 over the final eight minutes of the game. The Celtics were in the bonus for all eight of those minutes and took just four free throws. Both of those trips to the line were drawn on shooting fouls. There was just no attack from the Celtics to close out a victory that would have put them one win away from the Eastern Conference Finals.

The Celtics also turned the ball over five times in the quarter, leading to 10 Milwaukee points. This came after they had turned the ball over just five times over the first three quarters.

Udoka doesn’t escape the blame pie. He sat Brown for the first four-and-a-half minutes of the fourth quarter after Brown had cooked the Bucks for 16 points in the third. That may have been a little too long to keep him on the bench, and Brown was out of sync when he returned. He had just two shots in the quarter, and his only point of the frame came at the free throw line at the 6:48 mark.

A lot went wrong to close out Game 5, which has caused all the questions about whether or not the Celtics can close out a win to resurface.

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But again, the series isn’t over. It’s no easy task to knock off Giannis and the Bucks on their home floor, but the Celtics can do it. They just have to get back to playing Celtics basketball for 48 minutes. That is the difference between returning home for a Game 7, and returning home to clean out the locker room for the offseason. Staff