Manchester United are closing in on the signing of Ajax and Argentina centre-back Lisandro Martinez to the bolster the squad’s back-line that was a major weakness last season.
A €55m (£47m) deal will make the 24-year-old the second most expensive defender the club has ever signed, still a way behind Harry Maguire but marginally ahead of Raphael Varane.
A handful of vacant shirt numbers are available to Martinez, who has had an association with the number 21 jersey since he joined Ajax from Buenos Aires-based club Defensa y Justicia in 2019.
That shirt is unoccupied at Old Trafford and would be a seamless switch. It was last worn by Edinson Cavani prior to his recent release and has also been used by Daniel James and Ander Herrera. Aside from Cavani, Rafael da Silva and Diego Forlan have been other famous South Americans to wear 21 as United players.
However, that could also be a primary choice for Frenkie de Jong, who was Ajax's number 21 before Martinez and then went on to wear it for Barcelona as well.
Arguably a more position-appropriate number for Martinez is the now vacant six shirt left behind by Paul Pogba after his release and subsequent return to Juventus. He has previously briefly worn six for both Defensa y Justicia and the Argentina national team.
Another shirt from Martinez’s past at Defensa y Justicia is 24 and that is also vacant at United, left unoccupied since 2021. Darren Fletcher and Wes Brown are the only other players to wear it this century, while it belonged to David Beckham and Paul Scholes in the 1990s.
Argentine players have largely been popular with United fans in the past. Juan Sebastian Veron, Gabriel Heinze and Carlos Tevez all became cult heroes at Old Trafford, although the latter two left under a cloud due to the manner of their exits.
Marcos Rojo was less successful in more recent years, while goalkeeper Sergio Romero enjoyed a respectable run as David de Gea’s reliable understudy.
Other Man Utd squad numbers available to new signings
If 21, 6 or 14 doesn't take Martinez's fancy, he does have a number of other options open to him...