The Brazilian was outstanding in the last Barclays Premier League outing against Everton, picking up the man of the match award, and could be a contender for the club's Player of the Year award.
"I think so," Rafael replied, when asked by MUTV if this is his finest season. "I have played many games very consistently so it is probably my best season here.
"Of course, I think there are some games where I feel I could have done more - I should have done this or should have done that better. I definitely still want to improve."
The South American sat out the FA Cup tie with Reading on Monday after his exertions in the Bernabeu against Real Madrid when he was stretched in the first half but performed admirably after the break.
"I am just rested sometimes," he explained. "We have to rest so I'm happy because we won to stay in the FA Cup.
"I always want to play. I think every player wants to play in every single game but, when you're not playing, you can learn from things. I was there watching and can learn a lot.
"I think because it was a big game [against Real], I expected a lot more of myself and I thought I had to win every ball. I think I came out for the first half thinking like that. I thought, 'I need to win this ball' and, if I did something wrong, then I really had to win the next ball.
"At half time, the boss came to speak to me and I realised: 'Come on, it's the same as it has been all season. I don't have to win every ball.' So I