To cover the hypothetical scenario of United manager Louis van Gaal and executive vice-chairman Ed Woodward targeting Souare, here is a scouting report on the 24-year-old, 5'10", 150-pound Senegalese international.
Predominantly a left-back, Souare has the capacity to slot into midfield.
Like Rojo, he is a threat in the attacking half.
During the 2012 London Olympics, Souare created four of Senegal's six goals, per FIFA.
Souare registered more assists than stars such as Aaron Ramsey, Marco Fabian, Neymar and Pierre-Emerick Aubameyang.
Playing on loan at Reims, Souare swung in a cross for right-back Aissa Mandi, who redirected the ball past then-Ajaccio (now Malaga) goalkeeper Guillermo Ochoa.
Against Metz, Souare's first-time volleyed cross led to the ball falling fortuitously to Lille substitute Ronny Rodelin.
Souare's inventive backheel flick fashioned a chance for Lille centre-forward Salomon Kalou, whose shot led to Divock Origi scoring against Sochaux.
Souare's pass completion percentage rose by 3.3 percent last season—from 73.7 at Reims in 2012-13 to 77 at Lille in 2013-14.
Souare's current 90.4 pass completion percentage foreshadows extensive growth going forward.
Van Gaal envisions Rojo starting as a left-sided centre-back in a back three with the capacity to play as a wing-back or a full-back if United switch to a conventional back four.
Souare possesses the explosive athleticism to be converted into a centre-back for a three-man defence, a la Serge Aurier during portions of Toulouse's campaign last season.
Headed goals against Ajaccio and Montpellier show Souare's high vertical leap and his willingness to attack the ball.
Souare was in perfect position to clear Lyon attacking midfielder Clement Grenier's shot.
There are doubts over Rojo's defensive nous and the same applies to Souare.
Recklessness is an attribute embedded in Souare.
He dangerously followed through on Toulouse centre-back Dusan Veskovac and then-Rennes (now Al Jazira) forward Jonathan Pitroipa.
Souare conceded a needless penalty by sliding in from behind on Evian Thonon Gaillard midfielder Cedric Barbosa.
Unsurprisingly, Souare has never averaged 1.9 tackles or more in league play.
United have tabled a €20/£16 million bid for Rojo, per The Telegraph.
However, Rojo and Sporting are locked in a grudge-bearing dispute.
"There is no player bigger than the club," Sporting president Bruno de Carvalho said, per Sporting TV (h/t The Guardian). "I would not give up the honour, the club's history, for the attitudes of anyone. I give a piece of advice: don't use the press, be professional."
Souare has comparable traits to Rojo: 24 years old, physically impressive, left-footed and able to play two positions.
While not as polished as Ajax's Daley Blind, Monaco's Layvin Kurzawa or Wolfsburg's Ricardo Rodriguez, Souare should be on the list of secondary targets if Rojo's proposed move to United collapses.
Statistics via WhoScored