Nottingham Forest's hunt for new full-backs has seen them identify Joaquin Seys of Club Brugge or Leicester City's Victor Kristiansen for their left side of defence -- with Argentina international Nahuel Molina and RB Leipzig's Lutsharel Geertruida the leading candidates for the opposite side.
Nuno Espirito Santo, the Forest manager, wants competition for Forest's right-back, Ola Aina, and left-back Neco Williams, as well as a backup goalkeeper for Matz Sels.
That goalkeeper will be 32-year-old David Soria, currently with Spanish club Getafe, if Forest can land their principal target. Dominik Livakovic, the 30-year-old Croatia international, is a back-up option from Turkish club Fenerbahce.
Seys played in the Champions League with Club Brugge last season as well as earning his first call-up to the Belgium international squad.
However, it would not be straightforward prising him from Belgium bearing in mind his club have already sold another left-back, Maxim de Cuyper, to Brighton & Hove Albion. Club Brugge say there has been no contact from Forest over Seys, and they do not plan on selling the 20-year-old this summer.
If a move is too complicated, the 22-year-old Kristiansen is seen as a viable alternative.
Forest have been talking to Atletico Madrid about the finances involved to make a deal for Molina, a 27-year-old who has made 52 appearances for Argentina's national team.
Geertruida, a 25-year-old with 17 caps for the Netherlands, is next on Forest's wish-list if a deal for Molina cannot be arranged.
Despite opening talks via intermediaries earlier this summer, Forest appear to have accepted it would be too difficult to arrange a return to the City Ground for Matty Cash, five years after selling him to Aston Villa.
With the transfer window closing next Monday, Forest are also considering whether to return to Strasbourg with an improved offer for winger Dilane Bakwa. As The Athletic reported on Monday, Forest have already offered a package of €27.5million with €7.5m in add-ons but that was rejected by the French side as they are looking for more.
By Nottingham Forest correspondent Paul Taylor
The main source of Nuno Espirito Santo's sustained and often vocal frustration this summer has been his concerns over a lack of strength in depth in his Forest squad.
Having spent roughly £150million on seven new additions, there remains only a handful of positions in the side where the Forest manager is not now armed with at least two quality options.
Forest have hugely strengthened their attacking arsenal, with the additions of Dan Ndoye, Omari Hutchinson, Igor Jesus, James McAtee and Arnaud Kalimuendo.
If Forest can continue the same pattern of efficient recruitment that has been evident in recent weeks, by adding a new left-back and right-back, as well as another back-up goalkeeper, there will, in theory, be no more pieces of the puzzle left to fill.
In Ola Aina and Neco Williams, Forest possess two of the best full-backs to have played for the club in many years.
But even with their versatility -- both can play on either flank -- they cannot be relied upon to carry the burden of filling the full-back positions throughout a demanding campaign that will see Forest return to the European stage for the first time in three decades.
Forest will play at least eight games in the Europe League, and will find out who their opposition will be in the league stage of the competition on Friday.
You could see numerous members of the Forest coaching staff physically wince when Williams went down with an injury at Crystal Palace on Sunday.
Fortunately he was able to continue but, as Nuno again observed in his post-match press conference, Forest's current primary backup options are central defenders Jair Cunha and Morato.
Forest have already added free agent Angus Gunn as backup to golden glove-winner Sels, but Nuno would like a third option, with Forest having Soria and Livakovic as their main targets.
Nuno might still harbour valid concerns about the challenges of integrating new players into the squad, with the new season already underway.
But, that aside, if Forest can successfully land two of their quartet of full-back targets and another keeper in the coming days, it will address both of the manager's major sources of concern, when it comes to his squad.