Emma Raducanu has hit back "unfair" criticism over her mounting sponsorship deals following her early exit from the Miami Open.

The US Open champion was beaten by Katerina Siniakova in her first match in Miami this week after being given a bye into the second round.

Raducanu has only won four WTA Tour matches since she was sensationally crowned champion at Flushing Meadows as a qualifier in New York last September.

The 19-year-old has been in demand off the court and last week revealed she will be a brand ambassador for Porsche.

Briton Raducanu insists she is still driving high standards in training as she strives to build on her maiden grand slam triumph.

"Maybe you just see, on the news or on social media, me signing this or that deal and I feel like it’s quite misleading because I’m doing five, six hours a day [in training], I’m at the club for 12 hours a day," the 19-year-old told reporters.

"But I throw out one post in the car on the way to practice and all of a sudden it’s 'I don't focus on tennis'. I think that it is unfair, but it's something I have learned to deal with and become a bit more insensitive to the outside noise.

"At the end of the day, I feel like my days [with sponsors] are pretty limited. I'm not doing crazy days. I'm doing three, four days every quarter, so it's really not that much."