There is no denying that Juventus have endured a difficult start to 2015/16, this past weekend seeing them lose for the third time in their six Serie A matches to date.

Losing 2-1 away to Napoli on Saturday, they were particularly abject, lacking the cutting edge and leadership required if they are to return to winning ways.

Perhaps it was to be expected having undergone so many changes to the squad this summer, with the attack looking particularly blunt. Indeed, last week’s draw at home saw the Bianconeri set a new 10-year high for shots in a single game yet score only a single goal, per OptaPaolo:

However, the defence has been equally disjointed, conceding eight times in their first eight matches in all competitions and keeping just two clean sheets along the way.

It is a problem which has been addressed by boss Massimiliano Allegri after Frosinone’s 91st-minute equaliser proved particularly infuriating last Wednesday.

“I’m angry because we must improve quickly,” the coach said at a press conference immediately after that encounter, per the club’s official website. “At this moment we’re shipping goals from the first opportunity that falls our opponents’ way, you simply cannot concede from a corner with two minutes remaining.”

Andrea Barzagli was guilty of losing his marker on that occasion, and it was another poor defensive showing from the Turin giants.

The constant changes in midfield have, arguably, contributed to the woes of the previously solid back line, but seeking which pairing of central defenders is Juve’s best is remarkably straightforward.

Indeed, perhaps the Champions League final proved beyond all doubt that the Bianconeri are a much more difficult team to face when Giorgio Chiellini is part of the starting XI. His combative nature and infectious enjoyment of winning back the ball is transmitted to his team-mates, with the side looking stronger with the No. 3 included.

Chiellini enjoyed another fine season in 2014/15, with statistics from WhoScored.com showing he averaged 2.1 tackles, 2.6 interceptions and 5.1 clearances per game.

As the below graphic shows, he led the team combination of those three categories, further reinforcing his credentials as the rock of the side.

According to figures courtesy of Squawka.com, the 31-year-old won an impressive 57 percent of the tackles he attempted and 62 percent of all aerial duels contested.

Yet for the first time in a number of years his efforts were perhaps surpassed by a team-mate, with Leonardo Bonucci enjoying, arguably, his best-ever campaign.

Having previously struggled in a four-man defence, the former Bari and Pisa man was the biggest concern when Allegri opted to move away from the club’s 3-5-2 formation. Bonucci shrugged off those doubts with some superb performances, emerging as a true leader and a central figure in Juve’s success.

Figures taken from the WhoScored site show the 28-year-old averaged 1.1 tackles, 1.9 interceptions and 4.8 clearances per game in 2014/15, while also stepping forward into midfield and once again showcasing his impressive range of passing.

Thanks to the fact he is much quicker than Juve’s other central defenders, Martin Caceres has often made a case for regular inclusion, but the Uruguayan is injured too often to see that come to fruition.

Meanwhile, Barzagli has often complemented the aforementioned duo off the bench, allowing Juventus to revert to a three-man back line in order to protect a lead. But their coach also deserves credit, his tactical changes and relaxed approach making their own impact on his players since arriving last July.

“There’s been an immediate mutual understanding forged with Allegri,” Chiellini said at a media event last year—per the club’s official website—and that was reflected in the league and Coppa Italia triumphs.

However, it is undoubtedly the excellent on-field relationship Bonucci and Chiellini enjoy which marks them out as Juve’s best partnership in central defence.