One of the biggest fights on the card for tonight's UFC on ESPN 64 event in Mexico City has fallen through at the eleventh hour.

The middleweight contest between Kelvin Gastelum (19-9 MMA, 13-9 UFC) and Joe Pyfer (13-3 MMA, 4-1 UFC) has been scratched from the lineup just a few hours before the event after Pyfer fell ill.

"Just wanna say my heart is broken I couldn't fight today", Pyfer wrote on his Instagram stories. "I got super sick and hopefully we can reschedule this fight for a few weeks from now. Unfortunately comes with the territory of travelling outside the States. Never again. My apologies guys".

Gastelum, who won season 17 of The Ultimate Fighter prior to signing with the UFC back in 2012, had been set to make his return to the middleweight division after yet another ill-fated attempt at competing at 170 pounds.

The 33-year-old's career has been blighted by repeated struggles with the weighing scale, and after a catastrophic failure in his attempt to make the 170-pound limit for his last fight against Daniel Rodriguez last June, Gastelum was forced to accept defeat and return to 185 pounds this time around.

Pyfer, who has finished four of his five opponents during his impressive UFC run to date, will have been eager to add the name of a fomer middleweight title challenger to his impressive list of victims, but it appears he will have to wait a little longer for the opportunity to face Kelvin Gastelum.

Check Out The Updated UFC on ESPN 64 Fight Card Below

MAIN CARD (ESPN2/ESPN+, 7 p.m. ET)

  • Brandon Moreno vs. Steve Erceg
  • Drew Dober vs. Manuel Torres
  • Vince Morales vs. Raul Rosas Jr.
  • David Martinez vs. Saimon Oliveira
  • Kevin Borjas vs. Ronaldo Rodriguez

PRELIMINARY CARD (ESPN2/ESPN+, 4 p.m. ET)

  • Edgar Chairez vs. CJ Vergara
  • Ateba Gautier vs. Jose Daniel Medina
  • Melquizael Costa vs. Christian Rodriguez
  • Loopy Godinez vs. Julia Polastri
  • Rafa Garcia vs. Vinc Pichel
  • Jamall Emmers vs. Gabriel Miranda
  • Austin Hubbard vs. MarQuel Mederos