Dan Rafael reacts to the fight announcement for Canelo Alvarez vs. Amir Khan on May 7 and what this fight means for boxing. (1:00)

In a surprising move, middleweight champion Canelo Alvarez and welterweight contender Amir Khan finalized a deal Tuesday to meet for Alvarez's world title on May 7, Golden Boy Promotions announced.

The fight, made without even a whisper being leaked, will headline an HBO PPV card and take place at Alvarez's preferred contract weight of 155 pounds. That is five pounds below the middleweight limit and one above the junior middleweight limit. It is also an accommodation to the smaller Khan, a former unified junior welterweight titleholder who has been a contender in the 147-pound welterweight division since 2014.

"As the middleweight champion of the world, I will take on the best fighters in the sport, and on Cinco de Mayo weekend, I look forward to making the first defense of my titles," Alvarez said. "Amir was a decorated amateur, a two-time world champion and is in the prime of his career. Fans are in for a great fight on May 7."

Canelo Alvarez has won four fights in a row since a one-sided decision loss to Floyd Mayweather on Sept. 14, 2013. Al Bello/Getty Images

The site is not set but the fight is likely to take place at the new 20,000-seat T-Mobile Arena, which opens in April just off the Strip in Las Vegas. It would be the first boxing event to take place there and figures to draw a huge crowd given that Alvarez is Mexico's most popular fighter and the bout is taking place on Cinco de Mayo weekend, not to mention that England's Khan is likely to have tremendous support from Brits who will make the trek to the Nevada desert.

Alvarez won the middleweight world title by unanimous decision against Miguel Cotto on Nov. 21 in Las Vegas on a pay-per-view that generated 900,000 buys, second-most of the year behind the record-breaking 4.6 million sold by the juggernaut Floyd Mayweather-Manny Pacquiao mega fight on May 2.

But with Alvarez, the 2015 ESPN.com fighter of the year, due back in the ring for a May 7 interim fight before he squares off with unified titleholder Gennady Golovkin in the fall in what many view as the biggest fight in boxing, he needed a quality name opponent -- yet still one he will be favored to defeat to keep the Golovkin fight alive.

Khan fits the bill. He has a big name, good skills, fast hands and a following, not to mention a poor chin. Khan also wanted a big fight after having been strung along by both Mayweather and Pacquiao only to have them elect to face other opponents.

"I know Canelo fights the best and wouldn't pass up the opportunity to face me like others have," Khan said. "My goal is to always fight the biggest names and the best fighters. That is why I'm excited for this fight. Also, I would like to thank my team and Golden Boy Promotions for this opportunity. I know I have the speed and ability to beat him and will give my fans what they deserve on May 7."

Canelo Alvarez/Amir Khan odds Amir Khan +250 Canelo Alvarez -300 -- Westgate Superbook

So Khan will move up eight pounds for what figures to be a big-time event that was made despite the well-chronicled issues between Golden Boy Promotions and Khan adviser Al Haymon. Behind the scenes, Golden Boy CEO Oscar De La Hoya and president Eric Gomez were able to make the fight without dealing directly with Haymon, against whom Golden Boy has a $300 million antitrust lawsuit pending.

Although Haymon probably had to ultimately sign off on the deal, Golden Boy -- which used to promote Khan before he left when the company and Haymon had their acrimonious falling out in 2014 -- worked directly with Khan and Shah Khan, his father.

"We are committed to putting on the biggest and best fights in boxing," De La Hoya said. "Canelo is the biggest star in the sport and as he demonstrated against James Kirkland and Miguel Cotto last year, he is only getting better. Those who predicted that he would take an easy fight for his first defense have been proven wrong once again.

"As for Amir, he has won his last five fights including an incredible performance against Devon Alexander, and now that he is back where he belongs at Golden Boy Promotions, his future is very bright, once again."

Alvarez (46-1-1, 32 KOs), 25, a former unified junior middleweight titleholder, has won four fights in a row since a one-sided decision loss to Mayweather in their September 2013 blockbuster.

Khan (31-3, 19 KOs), 29, a 2004 Olympic silver medalist, won a junior welterweight world title in 2009 and made five successful defenses, including unifying two 140-pound belts. Since back-to-back losses, a controversial decision to Lamont Peterson in 2011 and a knockout loss to Danny Garcia in 2012, Khan has won five fights in a row but been relatively inactive with only one bout in 2013 and one in 2015.

But since moving up to welterweight in 2014, he has won all three of his bouts by clear unanimous decision, beating former titleholders Luis Collazo and Alexander at the MGM Grand in Las Vegas and, most recently, former junior welterweight titlist Chris Algieri last May 29 at the Barclays Center in Brooklyn, New York.