The Cleveland Cavaliers finished the regular season with one of the worst defensive records in the league ranked 29th.

They have struggled hugely on that end of the floor for a number of years now but it didn't hinder them in their run to the NBA Finals last season and another Eastern Conference Finals berth this time around.

It's almost impossible for a bottom two defence to win a championship and this could ultimately prove to be their downfall.

They face elimination to the Boston Celtics in their conference finals series as they trail 3-2 going back to Cleveland for a must-win Game 6 on Friday night.

The Cavs did well to claw themselves back from a 2-0 deficit as they showed a level of competent defence to protect their home-court.

But their defensive struggles returned in a 96-83 defeat on the road in Game 5 and their chances of progressing now look slim.

Their porous defence has been a major talking point all season and it's obviously something that opponents look to exploit.

In a recent interview with the "Pull Up" podcast, Portland Trail Blazers guard C.J. McCollum described the Cavs' rearguard as the worst he's ever faced.

"Cleveland is one of the worst defensive teams I've ever played against, honestly," McCollum said. "I think it's just the spacing.

"They've had a lot of different players on their roster throughout the season, so terminologies not the same, the continuity isn't always there.

"... So I think that's one of the reasons why their defense has been up and down. But then, when it's time to lock in and focus on one team, they're a lot better."

Change

The Cavaliers blew up their entire roster at the February trade deadline, offloading six players and bringing in four.

Isaiah Thomas, Dwyayne Wade, Jae Crowder, Derrick Rose, Channing Frye and Iman Shumpert were all traded and Jordan Clarkson, Larry Nance Jr., Rodney Hood and George Hill were acquired.

This move initially improved Cleveland defensively but they have fallen into their bad habits too often which points to an underlying problem.

But despite all of their turmoil this year, they are still just two wins away from making a fourth consecutive appearance in the Finals.

That's largely thanks to the greatness of LeBron James, who's enjoying arguably his best ever campaign in his 15th season.

The Wine and Gold will need him to produce magic once again if they are to overcome the 3-2 hole they're in against the Celtics.

LeBron's seven-year dominance in the east is on the line but he'll have the luxury of going back home for Game 6 where they've only lost once this postseason.

CLICK HERE to listen to Episode Two of the new GiveMeSport NBA podcast, featuring New York Times senior writer Marc Stein. Subscribe for all future episodes.