Barely 24 hours after welterweight titlist Shawn Porter destroyed former titleholder Paulie Malignaggi in the fourth round of a brutal, efficient and impressive performance to retain his belt for the first time on Saturday night at the DC Armory in Washington, D.C., he was put on notice about his mandatory defense.

Shawn Porter has 90 days to defend his IBF title against fellow unbeaten Kell Brook. Elsa/Golden Boy/Golden Boy/Getty Images

The IBF, which sanctions the belt Porter holds, sent a letter on Monday to Porter (24-0-1, 15 KOs) and Golden Boy Promotions, ordering his mandatory against England's Kell Brook (32-0, 22 KOs).

"Congratulations on your win over Paulie Malignaggi last Saturday, April 19, 2014 at the DC Armory in Washington, DC in an optional defense of the IBF welterweight championship," IBF championship chairman Lindsey Tucker wrote. "We wish you all the best for a long and illustrious career as the IBF welterweight champion.

"The IBF granted Golden Boy Promotions an exception to regulations for the Porter vs. Malignaggi fight. One of the conditions of the exception is that the winner must fight the leading available contender within 90 days. The leading available contender is No. 1 Kell Brook. ... Negotiations should commence immediately and be concluded by May 21, 2014. In the event that you are unable to come to an amiable agreement with Brook, the IBF will call for a purse bid."

The IBF furthe r ordered that neither Porter nor Brook can take another fight until the mandatory is completed. If Porter did, he would be stripped of the title. If Brook did, he would lose his mandatory status.

Golden Boy chief executive Richard Schaefer said he plans to discuss the Porter fight, among other topics, with Porter adviser Al Haymon when they are both in Las Vegas next week for the Floyd Mayweather Jr.-Marcos Maidana fight.

It remains to be seen whether Schaefer and Eddie Hearn, Brook's promoter, can make a deal.