The underperforming star is bound to be under a lot of pressure with arrival of attackers like Zlatan Ibrahimovic, Henrikh Mkhitaryan and the growth of Marcus Rashford.
Wayne Rooney have not performed consistently since 2013. Last season the English star scored just 15 goals.
He is even playing out of position since couple of year. Nowadays, the player generally from the central midfield position much lower to his natural place.
Wayne Rooney's performance will be heavily scrutinised by Jose Mourinho who is strict disciplinarian.
Speaking at a Gulf Oil event in Shanghai, Rooney said: "I think you always feel pressure when you play for Manchester United. It's one of the - if not the - biggest football clubs in the world.
"Always you feel you have to prove yourself each season. Of course there's pressure, there is always pressure to be successful."
The 30-year-old striker added: 'I'm excited. I think it's going to be a big season for us. The appointment of Jose Mourinho is a fantastic appointment.
"The signings we've made have been fantastic. Hopefully we can have a good start to the season and be successful at the end of it.
"I've only had one day (with him) before we came out but it was a very good training session. Look at the teams he has been at before and the success he's had.
"We're hoping he can bring in that success to us."
Manchester United are currently in China to play 3 pre-season friendly matches.