Robben, who has played alongside Boateng in six title-winning Bayern teams, indicated that he would be disappointed to see the World Cup victor leave the club. There are reports that there are negotiations going on behind the scenes between Boateng's management and PSG.
And the report claims the Red Devils were only willing to pay half of Bayern's asking price.More news: Arsenal vs Manchester City
Robert Lewandowski scored a hat-trick as Bayern Munich beat Eintracht Frankfurt 5-0 to retain the German Super Cup.
If the Bundesliga champions are to receive an offer for Boateng around €30m, then they should take the money and run. Former Dutch global Arjen Robben has warned the club's leaders not to underestimate Boateng's value to the team.
"That is the most important thing because we do have a lot of quality in our team". Otherwise, Robben is concerned about the team's success.
"For me Jerome is one of the best central defenders in the world", the Dutch winger said.More news: Greek teen Tsitsipas upsets Djokovic to reach Rogers Cup quarterfinals
United start their Premier League campaign on Friday at Leicester and, speaking on Sunday, Mourinho said: "My CEO knows what I want and I still have a few days to wait and see what happens. He is one of the world's best, and we need his physical presence on the pitch".
During his three-month injury break in 2016, Boateng was accused by Bayern officials of neglecting his recovery and participating in too many celebrity events.
The player stressed that the accusations were a great disappointment to him.More news: SCOTUS Nominee Brett Kavanaugh's Confirmation Hearing Scheduled