Arsenal and Manchester United have experienced contrasting starts to the 2026/27 Premier League campaign.
The defending champions sit second after winning four of their opening five matches under Mikel Arteta.
Arsenal also invested around £160 million during the summer, adding Bruno Guimaraes and Ezri Konsa among several new arrivals.
United, meanwhile, have collected only five points from their opening five league matches under Michael Carrick.
The Red Devils spent £155 million rebuilding their midfield but could turn their attention towards other positions in future transfer windows.
Both clubs are now assessing the same young defender as they continue planning potential additions to their squads.
According to CaughtOffside, Arsenal and Manchester United are monitoring Porto right-back Alberto Costa.
The report states that Manchester City and Paris Saint-Germain are also following the 22-year-old. Costa joined Porto from Juventus for €15 million plus up to €1 million in bonuses in July 2025.
He quickly established himself in Portugal, making 47 appearances and providing eight assists during his first season with Porto.
The Portuguese defender has remained prominent this campaign, starting five of Porto’s opening six matches across domestic and European competition.
However, none of his interested clubs have submitted a formal offer, with their interest currently remaining at the scouting and analysis stage.
Porto have Costa under contract until June 2030 and are therefore under no immediate pressure to sanction his departure.
His agreement also contains a €65 million release clause, providing Porto with considerable protection against potential suitors.
Juventus would additionally receive 10 per cent of the profit from any future sale.
Arsenal could value Costa’s ability to operate in different roles, while United could consider him as competition at right-back.
For now, Arsenal and United are continuing to monitor his development before deciding whether to advance their interest.
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