Brighton manager Fabian Hurzeler was livid as new signing Matt O'Riley's debut came to an end after just nine minutes following a horror challenge.
Denmark international O'Riley was later seen leaving the ground on crutches, with Hurzeler describing Williams' challenge as 'ridiculous'.
Hurzeler told Sky Sports: 'Ridiculous foul. It has nothing to do with football, we have to be honest.
'This situation changed a little bit the game because afterwards it's getting very emotional during this game but I hope it's not so bad.'
Brighton boss Fabian Hurzeler was livid with Jay Williams' challenge on Matt O'Riley
Hurzeler stated the left ankle injury suffered by O'Riley 'does not look good'.
'You can't tackle like this. It is a tackle where you take a risk of an injury of another player.'
Despite the early blow involving O'Riley, Brighton ran out 4-0 winners to progress to the third round of the Carabao Cup.
Simon Adingra, Jeremy Sarmiento, Adam Webster and Mark O'Mahony all scored. Crawley had substitute Jack Roles sent off in the second half.
Brighton's victory came off the back of Premier League wins against Everton and Manchester United.