The Portuguese tactician sat alongside Zlatan Ibrahimovic for the World Cup play-off clash at Friends Arena - fueling rumours he was assessing one of the two star players, who have both played alongside United's Swedish striker.
Forsberg was linked to Old Trafford last summer when Mourinho found that Inter were digging their heels in over his pursuit of Ivan Perisic.
The 26-year-old star is rated in the £50million bracket after making a name for himself as the Bundesliga's 'assist-king', but he signed a new contract to tie him to RB Leipzig until 2022.
Despite that, his agent stirred the pot in the summer by stating Forsberg's desire to leave Leipzig and Liverpool's pursuit of Naby Keita showed that persistence can pay off, albeit on the German club's terms.
Ibrahimovic was also a team-mate of Verratti for four seasons at Paris Saint-Germain and it would be no surprise if he has urged the Red Devils boss to sign the Italian.
The ex-Pescara starlet changed agents in the summer to link up with Mino Raiola's growing stable, which could also help Mourinho pull off a swoop for the 25-year-old.