Attempting to rid the sport of performance-enhancing-drugs (PEDs), the UFC signed a deal with the United States Anti-Doping Agency (USADA) last summer to implement a new and stricter drug testing program. When the partnership was first announced, now former UFC CEO Lorenzo Fertitta famously stated that “it’s going to get a lot worse before it gets better.” Perhaps he was right, as we’ve seen our fair share of fighters popped by USADA in recent memory.

In fact, we’ve seen two of the sport’s biggest stars notified of potential anti-doping violations in just the last few weeks alone. With that being said, it’s interesting to take a look back at USADA’s short history working with the UFC.

Whether it be the most shocking or the most impactful, let’s take a look at the six biggest busts by USADA in the UFC:

UFC Poland: Mirko Cro Cop excited to finally get "important ...6. Mirko Cro Cop

Legendary Croatian kickboxer Mirko Cro Cop made his return to the UFC on April 11, 2015 in a rematch with Gabriel Gonzaga. Cro Cop scored an impressive comeback victory over his Brazilian opponent, and he was next scheduled to face off with Anthony Hamilton at UFC Fight Night 79 in November 2015. That fight never came to fruition, however, as Cro Cop later pulled out of the bout and surprisingly announced his retirement from fighting.

It was then announced that the Croatian had been notified by USADA of a potential anti-doping violation. Cro Cop admitted that he had used Human Growth Hormone to help heal a shoulder injury, and it was later made clear that he had been suspended two years by USADA.

Despite being an ageing veteran, Cro Cop was attempting to make another run in the UFC, although that was ended when he failed his drug test.

Frank Mir5. Frank Mir

Frank Mir is a former multi-time UFC heavyweight champion, and one of the greatest submission artists in the history of the heavyweight division. After winning two straight bouts by stoppage throughout 2015, Mir was on his way back towards the top of the division, although a decision loss to Andrei Arlovski and a recent knockout loss to Mark Hunt set him back a bit.

On top of those two losses, Mir was recently notified by USADA that his fight day sample surrounding his fight with Hunt had tested positive for oral turinabol metabolites. The former heavyweight champion denied taking any performance-enhancing-drugs in the aftermath of the news.

Recently, Mir said that the appeal process was too expensive and that he would likely be taking his suspension. He also asked for his UFC release which could prove to be a somewhat upsetting end to a legendary career due to a failed drug test.

chad-mendes-ufc-fight-night-6314. Chad Mendes

Perhaps one of the more shocking USADA busts came when former multi-time UFC featherweight title challenger Chad “Money” Mendes was informed of a potential anti-doping violation last month on June 10, 2016. In the aftermath of the news, Mendes did respond via his official Twitter account, saying that “I own it and I’m going to pay for it.” It was then announced yesterday (July 20, 2016) that he had been suspended two years after testing positive for GHRP-6 (Growth Hormone Releasing Hexapeptide).

Despite losing three of his last four to the likes of former champion Jose Aldo, reigning champion Conor McGregor, and former lightweight champion Frankie Edgar, “Money” has proven to be among the elite at 145-pounds throughout his UFC tenure.

Yoel-Romero-Jeff-Chiu-AP3. Yoel Romero

Red hot middleweight contender Yoel “The Soldier of God” Romero has won seven consecutive UFC bouts including five by way of stoppage. During that stretch, he’s taken out some of the division’s top contenders such as Tim Kennedy, Lyoto Machida, and Ronaldo “Jacare” Souza. The former Olympian has likely done enough to earn a title shot, but a failed drug test has slowed his hype.

Last January, “The Soldier of God” was notified by USADA of a potential anti-doping violation in which he blamed a contaminated supplement for. As it turned out, Romero’s team and USADA came to an agreement in April on a six-month suspension due to the contaminated supplement.

Although Romero lucked out in terms of receiving a shortened suspension, he likely missed out on a title shot, and will possibly have to take another fight or two when he returns despite already being deserving of a shot at gold.

Brock Lesnar UFC 200 Weigh in2. Brock Lesnar

Former UFC heavyweight champion Brock Lesnar made his triumphant return to action after nearly five years away from the sport in the co-main event of July 9’s landmark UFC 200 card from Las Vegas, Nevada. As a surprise to some, Lesnar scored a somewhat dominant decision victory over legendary knockout artist Mark Hunt.

Due to his strong performance and enthusiastic attitude, many began speculating on a second UFC run for Lesnar, but that has now been put into question, as the former champion was notified last week of a potential anti-doping violation. Lesnar’s freakish physique has always drawn questions regarding PEDs, but until now, he had never failed a drug test.

Details regarding the test are currently unclear, but a two year suspension could very well end the 38-year-old’s second UFC tenure.

ufc 182 weigh-ins1. Jon Jones

Former UFC light heavyweight champion Jon “Bones” Jones is widely considered to be the greatest fighter of all-time, but his actions outside of the cage have always hindered him. “Bones” was stripped of his long-held title in 2015 after being arrested on felony charges, but was scheduled to attempt to recapture that title in the main event of UFC 200 against bitter rival and reigning title holder Daniel Cormier.

In shocking fashion, however, Jones was pulled from the highly-anticipated fight just three days prior after being notified of a potential anti-doping violation. Jones’ team quickly denied ever knowingly taking any performance-enhancing-drugs (PEDs), and it was just recently confirmed that he had tested positive for multiple estrogen blockers.

The former champion is currently temporarily suspended by the Nevada State Athletic Commission (NSAC), but his future is currently unclear. He and his team appear to be confident that a solution will be found, but at age 28, he’s also facing a two year suspension which would be devastating after missing the majority of 2015 due to legal issues.

Did we miss any major busts in the UFC?