Although it seemed pretty decisive towards the end of the fight, Vargas managed to sneak a hard right hand that stunned Khan right before the conclusion of the 11th round.
It was a clear and unanimous points victory against a tough but moderate opponent, but Khan was knocked down in the process and was noticeably exhausted in the later stages of the 12-round contest at welterweight.
The pace finally settled down as the fight entered the championship rounds with Khan continuing to be in control for the most part but still looking vulnerable to the overhand right which gave a bloodied Vargas some hope.
Hearn will meet Khan, Brook and Pacquiao's handlers in the next fortnight, disclosing that he may even attempt to purvey a two-fight deal with Pacquiao, the eight-weight world champion and serving senator in the Philippines. The rounds in the bank will do no harm but the defensive issues remain and that ensures any fight involving Khan remains must watch.
There was more drama in the third: Vargas was harshly given a count after he was caught by a cuffing right hand to the back of the head which sent him tumbling onto his back for the second time.
Vargas always felt he had a punchers chance but that was about it to be honest and Khan rightly had his hand raised after a fight which raised as many questions as it did answers for the future of one of the countries most famous fighters.
Khan used to train with Pacquiao, who holds a version of the WBA welterweight title, at Freddie Roach's gym in LA.
"I want to fight by the end of the year; 147 pounds is the division".
It's the 31-year-old's first fight at welterweight in over three years and promoter Eddie Hearn is already in talks with Pacquiao about a possible fight in December. Khan staggered backward but was saved by the bell once again. We will listen to the public, we know Amir wants Pacquiao and he will fight Brook. "Winning one more will be awesome for my career", he added.
"The only fight that works for me over Kell Brook is Manny Pacquiao". Although Khan showed heart, there was little on show to concern Brook.