He sees challenger Johny (Bigg Rigg) Hendricks as the hardest fight of welterweight champion Georges St-Pierre's career.
"But it also, by far, the hardest fight Johny's ever had," Sonnen adds.
Hendricks (15-1) is a former NCAA champion wrestler with one-punch knockout power. Jon Fitch, who went 25 gruelling minutes with St-Pierre in 2008, lasted just 12 seconds with Hendricks in 2011.
The former Oklahoma State wrestling star disposed of Amir Sadollah in 29 seconds, Charlie Brenneman in 40 and Martin (The Hitman) Kampman in 46.
St-Pierre (24-2) and Hendricks meet Saturday night at the MGM Grand Garden Arena in the main event of UFC 167, the UFC's 20-year anniversary show.
The 30-year-old Hendricks is a happy-go-lucky, gregarious father of three young girls who has shown his killer instinct this week in his choice of words, if nothing else.
"My mind is to kill him," said the Dallas-based challenger, before quickly adding: "Not in that sense, but it's to beat him, to demolish him. I want to win where he doesn't want to fight me again ... Yeah, he's done a lot of things, but that doesn't matter.
"When he steps into the Octagon with me, the past's the past. I plan on making a new future."
Of course, St-Pierre is used to having a giant target on his back. He has won his last 11 fights — the longest current winning streak in the UFC — while making eight straight title defences (former middleweight champion Anderson Silva holds the record at 10).
St-Pierre is a relentless machine whose performances in the gym would make an NFL scout drool. And the 32-year-old from Montreal is constantly adding new challenges to his training, be it working out with elite gymnasts or sprinters.
Muay Thai veterans Lamsongkram Chuwattana and Yod Wilek were part of his camp for Hendricks, helping break down the challenger's striking.
"Having Lam and Yod was a great blessing," said GSP coach Firas Zahabi, a former Muay Thai fighter himself. "Between the two of them, they have about a thousand fights. They have a keen eye. They watched Johny Hendricks, they analysed Johny Hendricks and they advised us greatly on many things, what to do, how to avoid the step-up power."
A southpaw, the five-foot-nine Hendricks' biggest weapon is his left hand. He can close distance at speed, launching himself at opponents and catching them going backwards. The stocky Hendricks also scores well in the clinch position, where he lands 37.8 per cent of his significant strikes.
Look to the five-foot-11 St-Pierre to keep his right hand tucked to his chin and fire off a left jab like a piston. He did it against Josh Koscheck, another former star wrestler with knockout power, and literally broke his face. Koscheck required facial surgery after his last loss to the champion.
The jab is a major part of the arsenal of any Zahabi fighter. St-Pierre uses it to tenderize his opponents, keep them away and to set up takedowns. Against Hendricks, he will look to make the most of a seven-inch reach advantage.
Hendricks' success with his fists has meant he has not had to resort to his wrestling much. But he took down Carlos Condit, a prickly striker, 12 times last out.
UFC president Dana White noted in the buildup to the fight that St-Pierre has been spending time on his standup game, while Hendricks — returning home to OSU for a number of training visits — has been concentrating on his wrestling.
While Hendricks was an amateur wrestling stud, St-Pierre is widely seen as the best wrestler in mixed martial arts. His 84 takedowns are a UFC record, as is his 75 per cent takedown accuracy rate. And he has stopped 88 per cent of his opponents' takedowns, the highest rate in welterweight history.
Often when two UFC fighters with the same strengths face off, the contest turns to a different area because it is hard taking on someone where they are at their best.
"Usually people take the path of least resistance," said Zahabi. "It's going to be hard for either one of them to take each other down. It's going to be about timing. It's not going to be about wrestling pedigree necessarily."
Since losing his title to Matt (The Terror) Serra at UFC 69 in April 2007 — he won it back the next year at UFC83 — St-Pierre has been taken down twice (both by Josh Koscheck who did it once in each of their two bouts) in 11 outings and scored 63 takedowns of his own.
In his last 11 fights, Hendricks' takedown count is 36-7 in his favour.
In addition to stuffing takedowns, St-Pierre is also good at evading punches. His 75.1 per cent significant striking defence rate in the highest in welterweight history and fourth-highest all-time.
Of course, Hendricks needs just one to connect. Serra, a 10-1 underdog, caught the freshly minted champion with a blow to the side of the head, disorientating him and then finishing him off.
St-Pierre had been distracted by family illnesses and the lures of being champion in the buildup to the Serra fight. He has not lost since.
While Hendricks has been growing as a knockout artist, the list of UFC fighters who have taken him the distance includes Condit, Koscheck, Mike Pierce, Rick Story (who beat him), Canadian T.J. Grant and Ricardo Funch. Three of his last five fights lasted the full 15 minutes each.
And now he faces five five-minute rounds for a championship bout.
It has been rare that St-Pierre has been pulled into deep waters, but he survived a nasty head kick from Condit to regain his senses and win the fight.
"He knows how to compete," Sonnen said. "If he's hurt, he pushes through it. If he's tired, he pushes it through it. If he gets put in a bad position, he recovers."
St-Pierre has been criticized for not finishing fights, although that may speak more to the shallowness of the critics.
The champion and his gold-standard coaching team are masters at breaking down opponents, looking to drag them where they don't want to go. Their goal is to win, rather than stage a highlight-reel finish.
Most elite fighters get that.
"He's very good on using strategy," UFC Hall of Famer Royce Gracie said of GSP. "He was saying earlier that people criticize him about his victories, that he's not finishing people.
"I think about the movie 'Gladiator.' There's a scene where the gladiator comes out and just wipes everybody out and the crowd gets silent. 'What's the matter? You're not entertained? Did I not put up a fight for you?' So people criticize. Get in there and do what he does. Go do what he does."
Said Sonnen: "He's just a guy that knows how to win, he understands strategy, he understand that the purpose is to get your hand raised, period. And nothing else. And don't make any apologies or excuses for that."
Hendricks, a state wrestling champion before he reached double digits in age, says he was raised in the cauldron of competition. Still, St-Pierre leads him 47-0 when it comes to UFC championship rounds.
The Canadian says pressure brings the best out of him, a fact his record supports.
St-Pierre is fighting for his growing legacy — he is tied with Hall of Famer Matt Hughes in UFC wins (18) and Silva in championship bouts won (11).
He trails Randy Couture by two for most championship fights (15) and Silva, by two, for most successful and most consecutive successful title defences (10).
And he is just 40 seconds from passing B.J. Penn's UFC fight time record of five hours three minutes 12 seconds.
Perhaps most worrying for his opponent, St-Pierre is on top of his game, according to his coach. Serious knee surgery in December 2011 is fully behind him.
"This has been the best training camp in the last three camps," said Zahabi. "It's much better than the (Nick) Diaz and the Condit camps. There was a lot of ring rust and I think that's why you see Georges so relaxed now. He had such great success in training, he was so dominant in practice, that I think his confidence really came back and he realized that 'Hey I did those two fights with a long layoff before. And the interval between Condit and Diaz was very short as well.
"I think he needed those two fights to come back to his level."
Hendricks is a tough competitor with several dangerous weapons. If St-Pierre can hold him off, take him deep into the fight and impose his will, it will go badly for the challenger.
"I won't believe anyone can beat Georges until I see them beat Georges," said Sonnen. "I think the world of Johny and all that nice stuff but Georges is the best fighter I've ever seen."
The bookies favour GSP, with odds between 2-1 and 3-1.