Sporting Lisbon full-back Pedro Porro is in London for a medical before a 45m euro (£39.5m) move to Tottenham.
Porro, who can also play as a wing-back, has three goals and 11 assists in 25 games for Sporting this season.
The 23-year-old Spain international, who has been linked with Spurs throughout the transfer window, was previously at Manchester City, though he did not play for the first team.
Porro joined Sporting from City for £7m last summer after two years on loan.
Although it is being stressed the transfer is not concluded and the structure is complicated, it is anticipated the deal will be complete before the 23:00 GMT deadline.
He would become Spurs’ second January signing after midfielder Arnaut Danjuma joined on loan from Villarreal until the end of the season.
Matt Doherty and Emerson Royal have been regulars on the right side for Spurs boss Antonio Conte this season.
Spurs also have Djed Spence, who joined last summer for a deal rising to £20m, but he has only played six times this season and has been linked with a loan move.
