The Brazilian midfielder has been linked with the Catalan giants since November having impressed in Gremio’s Copa Libertadores triumph.
If the move happens, Arthur will join a high-quality Barcelona midfield that already includes fellow Brazilians Philippe Coutinho and Paulinho.
Here, we take a look at three ways the 21-year-old could fit into the starting XI.
4-4-2
For large spells of the La Liga season, Ernesto Valverde opted for this formation following the injury of Ousmane Dembele.
With Lionel Messi and Luis Suarez spearheading the attack, the Catalan giants remain in safe hands – with the duo netting 44 league goals between them this season.
Behind the lethal attacking duo – Paulinho, Ivan Rakitic, Sergio Busquets and Andres Iniesta make up the midfield.
Arthur could come in on the left and replace Iniesta, or on the right and replace an in-form Paulinho.
In either position, the young Brazilian will have the flexibility to keep the ball rolling and always race into space to make himself available.
His composure on the ball from the left would be a significant boost to the Catalan giants’ attacking exploits.
4-3-3
If Dembele returns to the starting XI then Arthur – along with Coutinho – can play two possible positions.
The Gremio star could start on the left side of midfield – with Messi, Suarez and Dembele playing higher up the pitch.
This will allow Arthur to create chances from deep in a bid to unlock the elusive trio into attacking positions.
In addition, he could also start on the right wing and compete with the Frenchman for the position.
4-2-3-1
If Valverde was to opt for this new formation it would allow a devastating front four of Arthur on the left, Dembele on the right and Messi playing behind Suarez.
This would leave Busquets, Rakitic, Paulinho, Iniesta and Coutinho to fight for two central midfield roles in front of the defence.
An formation like this could terrorise any defence and give Arthur the freedom on the left to exploit space and provide open space for the likes of Messi and Dembele to run into and win possession.
