Jose Mourinho admits he is concerned with the state of Manchester United's readiness for the fast-approaching Premier League season.

Alexis Sanchez conceded he has struggled since joining "big club" Manchester United from Arsenal in January but wants to repay Jose Mourinho's faith after inspiring his side to a place in the FA Cup final.

Man of the match Sanchez headed a 24th-minute equaliser against Tottenham at Wembley on Saturday before Ander Herrera's strike after the hour sealed a gripping 2-1 semi-final win.

The Chile international joined United in a headline-grabbing switch during the last transfer window despite being heavily courted by Manchester City and has only scored twice in nine Premier League appearances for his new employers

"In truth it's been very hard for me, coming to a big club," he said, with a turn of phrase that might not go down particularly well in the red areas of north London.

"It changed everything so today I'm really happy, for the team, the goal and for the attitude we showed throughout the game."

Mourinho challenged Sanchez to keep doing the basics well to take his game to new heights following victory over Spurs and the 29-year-old revealed both men have taken time to adapt to their new working relationship.

"He is a coach who demands a lot, and when we lose he gets very angry," Sanchez said, indicating that Mourinho's irritation in the wake of the 1-0 defeat to Premier League basement boys West Brom last weekend was not merely for show.

"We need those kind of demands to get the best out of us. He asks me to play a free role, to enjoy myself, to attack, defend - to do everything!

"It's been difficult this season, I think next year we have to go for it. It was a tough change for me, the coach told me to speak with him, he's not used to bringing in players in January.

"It's been demanding but we hope to win the final. I have come here and I want to win everything next year with this team and with the coach."

An expertly directed finish beyond Michel Vorm from Paul Pogba's delightful cross means Sanchez now has eight goals in as many appearances for club and country at England's national stadium.

"It brings me good luck, I've scored a lot of goals here with Chile, against England, with Arsenal and now Man United, now I have another final to look forward to here," he added.

"It was great to win with Arsenal, and now with United, I demand more of myself every day and I am happy with the game and with the team.

"It was a great pass from Pogba, when the ball was in the air I wanted to hit it to the far post but then I saw the goalkeeper go the other way so I changed to the near post to catch him off balance."