Arsenal are reportedly leading the race to sign Ivan Fresneda ahead of Borussia Dortmund.
Both sides are reported to have submitted bids in the region of £13m, and the player was set to make a decision on Monday.
Football Insider reports that the Gunners are confident of winning the race for the 18-year-old's signature and making their third signing of the January window.
Mikel Arteta's side have already added Leandro Trossard from Brighton & Hove Albion and Jakub Kiwior from Serie A minnows Spezia, respectively, as they seek to maintain their Premier League title charge.
The report claims that once the transfer is complete, the youngster will be loaned back to Real Valladolid as the club already have Ben White and Takehiro Tomiyasu in the right-back position.
The Spain Under-19 international has featured 10 times in La Liga so far this season after breaking into the first team, and has attracted interest from across Europe, with Liverpool, Newcastle United and Manchester United also interested in the former Real Madrid youth player.