Liverpool forward Suso was fined £10,000 (HK$126,000) after labelling teammate Jose Enrique "gay" on Twitter.
Suso sparked protests last month when he posted a photo on the microblogging website of Reds defender Enrique having his teeth whitened and added a tweet which read: "What f**k is he doing? This guy is gay...he does everything except play football."
He later deleted the tweet and uploaded the photo with a different comment, saying: "I dunno what to say..."
But the Football Association, which earlier this year fined Ashley Cole £90,000 after the Chelsea and England star wrote a critical tweet about the governing body relating to the John Terry-Anton Ferdinand racism hearing, took exception to Suso's original comment and warned the 19-year-old about his future conduct.
The FA said: "Following an independent regulatory commission hearing ... Liverpool's Jesus Fernandez Saez (Suso) has been fined £10,000 and warned as to his future conduct for a comment posted on Twitter.
"The charge, which the player admitted and requested a paper hearing, was that he acted in a way which was improper and/or brought the game into disrepute in that the comment was posted on his Twitter account and included a reference to a person/s sexual orientation and/or disability."
However, Enrique took to Twitter a few hours after the punishment was announced and criticised the FA for fining Suso over what was intended to be a good-natured exchange between friends.
"Is amazing how FA can fine my friend Suso Fernandez for a banter thing. Was just a joke!!!" the Spaniard wrote.
Suso had made a promising start to his Liverpool career after moving to Anfield from Cadiz in the close-season.
The Spain Under-21 international has made 13 appearances for Brendan Rodgers' side.
Cole was punished after blasting the FA for casting doubt on his evidence at an FA hearing.