They don’t make sheet music for fights, but if they did, Georges St. Pierre’s performance against B.J. Penn Saturday would sound every bit as seamless as anything Mozart wrote.

The UFC welterweight champ used a concise mix of standup, clinch-grinding and ground work to wear down Penn en route to a stoppage after the fourth round.

Trainer Greg Jackson weighed in with Sherdog.com on the champ’s performance in his second title defense, which was perhaps his most impressive showing in a career defined by blowout performances.

“I couldn’t be happier. Georges is an amazing athlete and very intelligent,” Jackson said. “We wanted in the first round or two to do a lot of wrestling and get that lactic acid going. Go aerobic to anaerobic. Stay unpredictable.”

That’s exactly what St. Pierre did. Contrasting Saturday’s win with their first encounter in 2006, the Canadian showed a better mastery of standup against the wily Penn, using a stiff jab, closing the distance quickly to tie up against the fence and grinding the lightweight champ into an endurance test.

Despite Penn’s display of phenomenal takedown defense in the opening round, where he stymied several attempts by St. Pierre to plant him on the mat, the Canadian kept pressing and took Penn’s occasional counterpunches without visible reaction. Scoring repeated takedowns in the second and third, he displayed an astute sense of the ground game, pounding when openings were presented, all the while steering clear of Penn’s ultra-dangerous submission game.

“We wanted to stay unpredictable,” Jackson said of the strategy early. “There were a lot of little parts to it. We wanted to step out of B.J.’s guard, stand up, create space and drop heavy bombs. The overall game plan was to use speed, unpredictability and get him tired.”

The fight became increasingly one-sided by the third round as St. Pierre’s top pressure and seamless ability to pass to side control, and even mount, allowed him to hammer Penn at will. After a brutal stretch of strikes in the fourth round, Penn returned to his corner and got a long look from the ringside physician prior to his cornerman stopping the bout. It was a game performance by Penn, whose often-questioned conditioning carried him through the equivalent of a 20-minute train wreck.

“I thought it was a smart idea to stop it,” Jackson said. “B.J. is a true warrior. I didn’t think they were going to stop it, but I’m glad.”

Penn was able to keep a tight guard when taken down early, even setting his legs high up on St. Pierre’s back. The 170-pound champ seemed a move ahead, though, picking his spots to strike and staying away from Penn’s wily setups. Penn didn’t break in any one spot but was simply beaten down as St. Pierre pounded whatever was available. The bigger fighter exerted crushing pressure on the ground and made Penn constantly work to compete and, ultimately, to survive.

“I was never worried, but I was always concerned,” Jackson said of the fight. “B.J. is an amazing fighter and a super tough guy. He has a warrior’s heart. I have the utmost respect for him.”

St. Pierre’s next defense is expected to be against Thiago Alves, a hard-charging welterweight who matches him in natural size, with potent striking and improved takedown defense as well. Jackson looks at it as another challenge that will require a fresh game plan.

“A super big threat. Very powerful, very strong and kicks incredibly hard, good jiu-jitsu,” he said of Alves. “He represents an amazing threat to us.”