Sometimes, it can be difficult to definitively measure the effect of a partnership. For example, not many would demur from the opinion that Patrick Viera and Emmanuel Petit were important to the success of the Arsenal team of that era, but just how important? Bergkamp, Henry, Seaman, Dixon and Adams were also major cogs in the machine that helped to make the team work efficiently. What about Roy Keane and Paul Scholes of Manchester United of broadly the same era? Did they contribute more to the success of the team than, say, Ronaldo, Rooney, Giggs or Beckham?

Looking at partnerships in some areas of football and evaluating their importance can be a little tricky. At the sharp end of things, both in scoring goals and keeping them out though, there are a plethora of numbers to define things. This is certainly the case with the pair being celebrated here. The rock-hard centre of Jose Mourinho’s first double-title winning Chelsea team – John Terry & Ricardo Carvalho.

When Mourinho blustered his way into Stamford Bridge, Terry was of course already a part of the furniture there but, as in the eternal wisdom of building a successful team from the back, the new Portuguese manager saw there was a gap to fill in the centre of the Blues defence alongside the skipper, and realised that if he could find the perfect foil to dovetail with Terry’s qualities, it would go a long way to keeping the back door of his team locked, and double-bolted.

At the end of the previous season, with the warm glow of Champions League winners’ medals hanging around their necks, a number of Porto’s players were set to leave the Estádio do Dragão in the wake of their manager decamping to West London, and Ricardo Carvalho was one of the top targets for Europe’s elite clubs. On top of the successful run to Europe’s premier club trophy, the defender had enhanced his reputation even further with a number outstanding performances in the Euro 2004 tournament, earning himself a place in the UEFA Team of the Tournament. Barcelona, Real Madrid, Inter Milan and Manchester United had all been linked with the player, but Mourinho knew that this was the guy he wanted to form a partnership with Terry at Chelsea, and swooped in with £25million to secure the deal. A few years down the line it looked like money exceptionally well-spent.

To many, it first seemed however as though the fit was less than perfect. The Portuguese defender, not unusually for any number of players arriving in the Premier League, had difficulty adapting his play to the English game, and was dropped from the team. A couple of unwise comments to journalists from the player, describing the decision to omit him as “incomprehensible” brought a typically spikey response from the manager that, “Carvalho seems to have problems understanding things, maybe he should have an IQ test.” He also fined the player and left him out of the squad for the following game. The sanction seemed to work though and in September he returned to the fold, slightly chastened and a fair bit wiser. His form improved and the partnership with Terry blossomed. They became the bedrock of the team’s defence.

As with so many successful parts of a football team, partnerships between centre-backs rely on differences more than similarities. Looking at similarly successful pairings across the same era, the validity of that assertion is borne out repeatedly. Vidic and Ferdinand were fundamental to the continuing success of Manchester United under Sir Alex Ferguson. Vidic, the no-nonsense Serb was the stopper; the man who would challenge in the air and on the floor, tackle robustly and be the hard man. In comparison, Ferdinand of course was no blushing flower and could certainly handle himself in physical confrontations, but also had the ability to read a game, the positional sense to cover and sweep up around Vidic, and the technical ability to bring the ball forward, knowing that his mate had the back door covered. It was not a dissimilar situation with Terry and Carvalho.

For Vidic, read Terry. That ‘Captain, Leader’ Legend’ oft-quoted phrase sums up the Chelsea stalwart’s approach to defending. Brave as a lion and the sort of player that you look at and know that he really enjoys defending. Again, a comparison with Vidic is valid here. Both players would be hated by their opponents’ fans but lauded to the hilt by the faithful of their own clubs. Carvalho, though slightly different in both stature and approach to Ferdinand, nevertheless was also the ideal counterpart to the guy alongside him in the defence.

Much shorter than the Manchester United captain, Carvalho also appeared a slighter figure, but any forward who tangled with him would testify to his street-wise nous of the game and willingness to indulge in some of the darker arts of defending when the need arose. He was also blessed with the pace of a striker and as well utilising this asset in defence, also had the temerity to be one of the first in line for any swift counter-attacks when the opportunity arose. The concluding goal in the 3-0 rout of Manchester United at Stamford Bridge to give Chelsea back-to-back titles is a nice example.

For all that however, a partnership perceived to be adroit by the coach is one thing, for it to be truly effective on the pitch, the players need to believe in it too. Carvalho was certainly convinced. Talking to ‘Chelsea’ magazine, he spoke of his early times with the club and how he felt the early symbiosis between himself and the team captain. “In my first year here, it was hard for me because I was at a new club, in a new country, in a new league and playing a much more physical kind of game than I was used to in Portugal,” he said. Such obstacles are often the catalyst for progress however, and that seemed to have been the case here.

“JT recognised this straight away and was such a big help, on and off the pitch,” Carvalho went on to say. “He really made me feel comfortable. He is one of the best I’ve played with and a great leader too.” The Portuguese also appreciated the importance of having compatible styles. “He is stronger than me and likes to get in the air whereas I play more with the ball than him. But that is what makes us such a good partnership together. As a centre-back, whoever you are playing with, you have to know your partner very well and have an understanding. It’s like being two halves of the same whole. Instinctively, I have to know what he is going to do and he has to know what I’m going to do. The understanding between the two players is very important.” In kind, Terry would reflect that playing alongside his Portuguese partner was a key element in both his, and the club’s, success.

It would be wrong however to say that Carvalho was the only successful partner Terry had at the time, William Gallas was also a prominent factor in the role alongside his captain, although the excellence of Carvalho often meant that the Frenchman was shunted out to a full-back position. Terry’s assessment of his partner was probably best illustrated a couple of years ago when a national newspaper invited him to select his best Chelsea XI from the team-mates he had played with. Choosing himself at centre-back, Carvalho was his selected partner.

Earlier I mentioned how with defensive partnerships, it’s perhaps easier to illustrate success with quantitative evidence, and therefore after considering the various qualitive points above, let’s look at some figures and see how they stack up in support of the assertion that here was one of the greatest defensive partnerships of the Premier League era. A review of the first season the two were paired for any length of time in the Chelsea backline reveals some outstanding statistics.

In the 2004-05 season, across 38 Premier League games, the Chelsea defence shut out the opposition on no less than 25 occasions. That’s almost exactly two-thirds of all league games, and something that is actually as astounding as it sounds when it’s first read. Read it again, and then take in the implications. The club’s defensive record at home though, perhaps puts even that into the shade. In 19 league games they conceded just six goals at Stamford Bridge. Across the Premier League era, not only is that the best record, it’s far and away the best record. None of Manchester United, Tottenham, Liverpool, Manchester City, Everton or Arsenal could break through the Blue wall of Terry and Carvalho at Stamford Bridge and the only goals conceded were against Birmingham, Bolton, Crystal Palace and Fulham, none of which were even vaguely in contention to challenge for the title. Against all of their major rivals, the home defence – with Terry and Carvalho at its heart – was as stingy as the Chancellor of the Exchequer on the severest of austerity drives. Having the back door locked so securely allowed the club to accumulate 95 points in that season, a Premier League record.

This was no ‘one-season-wonder’ performance though, and into the following term, there was no sign of any let up. In fact, a national newspaper offered a ‘reward’ of £10,000 to the first player who could lower Terry and Carvalho’s flag. All through August and nearly to the end of September, the money was safely ensconced in the safe at the newspaper’s office. It was only in the last game of September that Aston Villa’s Luke Moore breached the dam. It had taken almost ten hours of playing time into the new season for it to happen, but eventually, the cash had to be coughed up.

Doubtless, some will say that although the achievements of the Chelsea backline were indeed laudable, it should not be the case that the Terry-Carvalho axis receives all of the credit. That’s a perfectly valid point of course, and having a goalkeeper like Petr Cech, full back support from Paolo Ferreira and Gallas, plus the exquisite covering play of Claude Makélélé in front of them helped more than somewhat. Plus, the attacking qualities of the team tended to mean that play was often concentrated in the other half of the field.

All those things are indeed relevant. It’s equally relevant however to bear that in mind when considering the merits of any partnership in a team of eleven players. No strikers can thrive without a midfield to support them and supply opportunities, and the value of any midfield pairing is even more reliant on the other components of the team. Yes, it’s true that Roman Abramovich’s roubles had assembled a stellar cast of players who all played their part, but at the heart of that backline was the Terry and Carvalho partnership, proving to be the very hardest of nuts for the opposing teams to crack open. All tried. Most failed.

Opinions are the very lifeblood of football of course, but here I’ve illustrated the worth of the Terry and Carvalho partnership through both qualitative and quantitative assessments, so let’s leave the summing up to a player who was not only a prominent player in the same era, but also knew more than a fair bit about the value of defending himself. Last year, Jamie Carragher was invited by a national newspaper, to assess the best ten centre-backs in Premier League history. Not only did he place Terry as his number one choice, he also placed Ricardo Carvalho at number five. It was the highest ranking of any pair in Carragher’s list and stands as a fine testament to the rock hard centre of Chelsea’s defence at the time, the indomitable pairing of John Terry and Ricardo Carvalho.

(This article was originally produced for the ‘Duology’ series on the ‘These Football Times’ website).