There are few players like Chelsea's César Azpilicueta. The Spaniard is hard-working, likeable, versatile and, most importantly of all, incredibly talented.
Since his £7million signing from Marseille in 2012, the 27-year-old has established himself as one of European football's finest defenders. But unlike many of his contemporaries, Azpilicueta has developed his reputation while being shunted from position to position.
His Chelsea career began as a right-back but he was moved to the opposite flank by José Mourinho. And as a left-back Azpilicueta helped the Blues clinch the Premier League title in 2015.
He became one of the most reliable full-backs in England but another positional change occurred this season when Antonio Conte moved to a back three.
Azpilicueta was deployed as a centre-back and took to the role instantly. He may not possess the height of a traditional central defender but his reading of the game and recovery pace allowed him to thrive.
Another Premier League title followed. And then, as with many a Spanish player who has impressed in English football, Barcelona's interest was aroused.
The Catalans are in need of a reboot this summer and no more so than in defence. It's why their interest in Azpilicueta is entirely logical.
If Barça were capable of luring him away from Stamford Bridge, and that's a very big if, they wouldn't be gaining just one defender, they would, in effect, be gaining three.
It's the position Chelsea signed Azpilicueta to play but one that has hasn't featured regularly in since the 2012/13 campaign.
That season, his first at Stamford Bridge, the Spain international made 48 appearances across six competitions at right-back. The man nicknamed ‘Dave' won over the Blues faithful with a number of consistent displays.
In the Premier League he completed 2.6 tackles per game, 1.6 interceptions and 2.5 clearances. Not bad for a player who was still engraining himself in a different league, culture and club.
Those statistics compare favourably against those of Barcelona's right-back last season, Sergi Roberto.
The 25-year-old is a central midfielder by trade but was slowly moulded into a full-back by Luis Enrique for two reasons.
The first was that the Catalans were unable to find a natural replacement for Dani Alves and needed an effective stop-gap. The second is that, despite his ability, there wasn't a space in midfield for Roberto.
He either had to adapt or move on. The Spain international choose the former and made a good fist of it. In LaLiga, Roberto averaged two tackles a game, 1.5 interceptions and 0.9 clearances.
His passing, as you'd expect from a natural midfielder, was more accurate compared to Azpilicueta but there's little doubt the Chelsea defender would be a defensive upgrade on Roberto if Barça were able to convince him to leave west London.
It was early into the 2013/14 season that Azpilicueta's first positional change occurred. Mourinho had returned to Stamford Bridge with a clear plan of how to add another Premier League title to his CV.
But that plan, to begin with, didn't contain Azpilicueta. Interesting the 27-year-old didn't start any of the Blues' first ten Premier League games that season. In his way was Ashley Cole, one of, if not the, finest left-backs to played in England's top flight.
But Cole was an ageing force and Mourinho soon realised it. He drafted Azpilicueta into the left-back role in mid-October and, unsurprisingly, he soon made it his own.
By the following summer, Cole was deemed surplus to requirements and left the club on a free transfer. Azpilicueta won the Premier League title the following season, keeping Filipe Luís, who was signed in the summer of 2014, on the bench.
The 2014/15 campaign was Azpilicueta's finest as a left-back. In the Premier League he averaged 3.4 tackles per game, 1.7 interceptions and 3.1 clearances.
When you compare those figures to Barcelona's current left-back Jordi Alba, who was in and out of the side last season, there is no contest.
Alba, an excellent attacking full-back, averaged only 1.2 tackles and interceptions per game and made 1.7 clearances.
His six assists, however, are double of that made by Azpilicueta's during the 2014/15 Premier League season.
So new Barcelona boss Ernesto Valverde would prioritise defensive solidity over creative attacking play if Azpilicueta usurped Alaba in the Barca starting XI.
Playing as a central defender was the latest addition to Azpilicueta's ever-growing repertoire.
It was at the start of October that Conte introduced the 3-4-3 shape at Chelsea and that meant Azpilicueta was shifted inside from the left-flank for the first time in over three years.
He was stationed on the right of Chelsea's back three and won a number of plaudits given how easily and instantaneously he adapted to the role.
In the Premier League this season, which Chelsea won by seven points, Azpilicueta averaged 2.2 tackles, 1.9 interceptions and 3.1 clearances per game.
He also played every single minute of the Blues title victory, becoming only the fourth outfield player in a title-winning side to have done so.
But how does he compare to Barcelona's current first-choice centre-backs of Gerard Pique and Samuel Umtiti?
In LaLiga, Pique made an average of 1.7 tackles, 1.5 interceptions and 4.2 clearances per game. Umtiti averaged 1.1 tackles, 1.9 interceptions and 2.7 clearances.
Neither match Azpilicueta's all-round defensive contribution but the Catalans' centre-backs are simply not having to work as much without the ball as the Chelsea star
Barcelona often dominate possession and build from the back. That must be taken into account. Pique made an average of 69.5 passes per game last season and Umtiti wasn't far behind with 68.3.
By comparison, Azpilicueta, as part of a back three, made 64.8 but his pass success of 87 per cent was lower than Pique (90.2) and Umtiti (92.9).
If Azpilicueta was to be brought in to play centre-back he'd face a fight on his hands to earn a first-team place. But history suggests it would be a battle he eventually wins.