Arsenal scouts were in San Sebastian on Wednesday night to watch on Real Sociedad's Champions League game with Benfica, 90min understands.
There were a number of players of interest on show at the Anoeta Stadium, but sources have told 90min that the main reason for their presence was to check on the progress of Martin Zubimendi.
Zubimendi, a previous transfer target for Real Madrid and Barcelona, is emerging as a potential option for Arsenal ahead of the January transfer window as they look to bolster their midfield options.
The 24-year-old is contracted to Sociedad until 2027 and has a release clause of €50m (£43.6m).
Zubimendi was not the only player of interest to Arsenal, with Benfica also fielding both Joao Neves and Florentino Luis - two players they have previously looked at.
Bayern Munich, Borussia Dortmund and Paris Saint-Germain also had a presence on Wednesday.
90min understands that Bayern in particular were at the game for similar reasons to Arsenal, checking in on Zubimendi and Neves, both of whom they have been tracking on for some time.
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This article was originally published on 90min as Arsenal scout Real Sociedad star also tracked by Bayern Munich.