Hatton was pushed all the way to a points decision by his Argentinian opponent on a frustrating night at Manchester's MEN Arena.
The result was never in doubt with the three ringside judges scoring 119-108 (twice), and 120-107 to give Hatton his 36th successive professional win.
But Hatton lacked a killer punch and admitted his performance was not good enough.
Hatton, then 25, said: "To be honest I felt really comfortable – never once did I not feel in control or losing my grip. But I felt flat and tired, it was an under-par performance.
"I don't have too many bad nights but you can mark one down for tonight. That was a little bit below average."
Hatton did drop Vilches to the canvas with a fine-looking left hook in round five but referee Darryl Ribbink deemed it a low blow and gave the challenger time to recover.
For the majority of the remainder of the contest Vilches hung on determinedly and largely succeeded in silencing another five-figure crowd.
Vilches looked determined to make a fight of it and dealt well with a cracking left uppercut from the champion midway through the first round.
Vilches got the chance to open up a little in the third but lacked the power in his punches to change the course of the contest.
For a moment in the fifth round Hatton appeared to have got his man but Vilches got up after his brief respite and hung on, firing a number of unpunished low blows of his own in the later rounds.
The crowd got on his back and cheered Hatton's desperate attempts for a late knockout but the Englishman had to settle for a points win.