HITC Sport understands that Boro are pushing to process the relevant paperwork and receive international clearance.
The 23-year-old has been recommended to Boro by the same people who brought them Christian Stuani - who has settled in well at the Riverside Stadium following his summer move from Espanyol.
Now Boro could add a second Uruguayan to their squad in the shape of De Pena, who has spent his entire career to date with Montevideo-based Nacional.
Paperwork and international clearance has been holding up the move and Boro sources have confirmed to HITC Sport that it could be a race against time to get everything done and dusted by the 6pm deadline.
Boro are also understood to be looking at other options and have not ruled out bringing in a couple of new faces on deadline day, although they do have the fall back option of the loan market if they do not get the players they want in the next few hours.