UFC Fight Night: Diaz vs. Guillard (also known as UFC Fight Night 19) was a mixed martial arts event held by the Ultimate Fighting Championship (UFC) on September 16, 2009 in Oklahoma City, Oklahoma.

A previously announced bout between Josh Neer and Kurt Pellegrino was moved to UFC 101.

Justin Buchholz replaced an injured Ronys Torres in a bout against Jeremy Stephens.

Ed Herman was supposed to replace an injured James Irvin against Wilson Gouveia at UFC 102 but then Gouveia suffered an injury. Herman instead faced Aaron Simpson at the event.Dan Miller was set to replace Herman. However, an injured Miller was replaced by Jay Silva against CB Dollaway.

An injury forced Chris Lytle off the card.Jake Ellenberger replaced him.

Kyle Bradley pulled out of his matchup with Sam Stout due to injury and was replaced with Phillipe Nover. However, on the night of the fight, Nover suffered from a seizure in the locker room. His match against Sam Stout was cancelled as a result.

This event served as a lead-in to the premiere of The Ultimate Fighter: Heavyweights on Spike.

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Wikipedia