Nuno Tavares will undergo a medical with Arsenal this week.
The Gunners have agreed a deal with Benfica worth an initial €8m.
A Portugal U21 international, left-back Tavares has been brought in as cover and competition for Kieran Tierney.
Mikel Arteta was left short at the position last season and doesn't want to make the same mistake again.
Tavares accrued 30 appearances for Benfica after making his debut in August 2019.
