Jorginho, Jean-Michael Seri, Sergej Milinkovic-Savic, Toni Kroos, Arturo Vidal, Fabinho and Mateo Kovacic have all been mentioned as potential targets.
But according to Spanish media outlet Diaro Gol, Mourinho views Rakitic, who joined Barcelona in 2014, as the ideal man to fill the missing piece in his midfield jigsaw.
Watching Rakitic can be a joyful and frustrating experience: the Croatian has a natural feel for the ball at his feet and passes beautifully through the lines, but at times of high intensity or when playing against a deep press – the game against Chelsea serves as an example – his footballing intelligence comes under question.
Sometimes his positioning, and specifically how he receives and lets go of the ball, can often look caveman-like alongside Andres Iniesta and Sergio Busquets. Too slow, too uninventive, too transparent.
Then again, they are Andres Iniesta and Sergio Busquets, and United would unquestionably have more quality in midfield with Rakitic in the side.