It is the 26-year-old’s first season in La Liga with newly promoted Rayo and the Old Trafford boss is thought to have sent chief scout Martin Ferguson to watch him in their game against Real Madrid last weekend.
The Spaniard has been putting in some impressive performances at full-back for the Madrid side and the report suggests Red Devils appear to have taken notice, something that Tito is happy to hear.
“It's really flattering that a club like Manchester United are looking at me,” he told AS.
“I already knew that Martin Ferguson was here on Sunday at Vallecas because they told me in the dressing room.
“What I don't know is if that possible interest from the English club will translate into anything more in future.
“If it does, I will de delighted. And if not, I will continue at Rayo, where I am happy.
“But [these things] are always pleasant for a footballer. It's the result of the hard work put in by the whole team and the good season we are having.”
Interest from one of the world’s biggest clubs completes an incredible change in fortunes for the right-back.
Before joining Rayo in 2009 he had been playing for lower division teams and also had a spell with RCD Mallorca B squad.
Rayo are back in Spain’s premier division after an absence of eight years and currently lie in 11th place.