Samsung is sponsoring the Mutua Madrid Open tennis tournament that begins this weekend, thinking it will get plenty of opportunities to market to budding fans. But one Samsung-sponsored celebrity tweeted out his endorsements for the Galaxy S4 from none other than an iPhone 5, in yet another embarrassing marketing moment. 

Our poor victim was Spanish tennis player David Ferrer, who sent a Galaxy S4 loving tweet to his more than 350,000 followers, but it was conveniently labelled as "via Twitter for iPhone". The tweet read "configuring S Health on my new #GalaxyS4 to help with training @SamsungMobile". But we wonder if that was really the case, as the iPhone seems to be his thing if his Twitter timeline is any indication. 

A similar situation occurred with star singer and BlackBerry brand ambassador Alicia Keys who, while quoting some fresh Drake lyrics, made the mistake of tweeting from her iPhone. Keys had been tweeting from her BlackBerry Z10 since launch (where she was pulled on stage), before making the awkward mix-up - perhaps hinting what her personal phone of choice may be. 

The case of Ferrer is yet another example of Samsung's humongous marketing budget to lure customers away from Apple. It notably started with the Galaxy S3, resulting in other celebrity endorsements and a bevy of advertising attacking the folk who endorse the smartphones out of Cupertino. Samsung is presumably thinking: "if a celebrity endorses our health product, health-conscious customers will jump on board with our smartphones."

Ferrer has since deleted the tweet, but a screen grab was saved by the Huffington Post.