The United boss cited the example of Switzerland's favourite son - who is an eight-time Wimbledon champion on grass but has also claimed Grand Slam titles on hard courts and clay.
Striker Marcus Rashford should be involved against Young Boys as he's now serving a three-match Premier League ban but there was no sign of Antonio Valencia or Jesse Lingard at Manchester Airport today so it looks like the duo have been rested.
Reports in the British media this week suggest Rashford is set to weigh up his options due to his frustrations over a lack of first-team football.
"I just think there is a balance".
"I don't think it's too far Mourinho's fault and too far Rashford's fault".
The match at the Stade de Suisse will be played on an artificial surface, but Mourinho said: "We are in Switzerland, the home of one of the best ever tennis players [Roger Federer], and I'm pretty sure that the big man sometimes is not happy to play on such a surface, but he has to play and has to win". I like Danny Welbeck as a player, and I hope this doesn't come across disrespectfully - Marcus Rashford does not want to become the next Danny Welbeck. "Apart from that, we go with everything we can, and we have to try to win".
"I just want to remind you, in advance, that we can only start with eleven [players] so when you see the team you could try to speak about the ones that are going to play and not the ones that are not going to play", he said.
"The reason I said what I said is because I am talking about Rashford in terms of a centre-forward".
"You can bring in Lukaku, you can bring in Sanchez". I'm Manchester United, I'm Manchester United through and through.
Rashford scored eight goals in 18 games in his first season in the Manchester United team under Louis van Gaal.
Jose Mourinho has told Manchester United to be inspired by Roger Federer and ignore concerns over the pitch in their Champions League meeting with Young Boys.
But Hargreaves believes a move away from Old Trafford would not be beneficial to the England global.