"I became his Marine drill instructor," Salazar said.
With Centrowitz unable to do much running -- even at the end of May he was only running between 25 to 40 miles per week outside -- Salazar put him through a punishing cross-training regimen.
Salazar had Centrowitz on a stationary bike, in the swimming pool, on elliptical machines. He pushed him through an exhausting series of calisthenics.
"I really worked his butt off," Salazar said.
After grueling training sessions in the gym, Salazar would make Centrowitz churn three miles uphill to the condominium in which they were staying. The elevation was 7,000 feet at the base of the hill, and 8,000 feet at the condo.
Still, it wasn't clear that Centrowitz would be ready for the Olympic Trials.
"He didn't do any speed work until about May 15th," Salazar said. "I told him, 'You've got to start running fast. If you don't do it now, you're going to have no chance.'"
Salazar said that doctors assured him that Centrowitz wouldn't structurally damage his knee by running hard. There would, however, be pain.
"He just had to push through it," Salazar said.
During Salazar's "boot camp" Centrowitz was so worn out, he was sleeping about 14 hours a day.
At one point, Salazar said, Centrowitz told him he was exhausted.
Salazar remembers telling him: "Tired? You're tired? Matthew, there is no tired in distance running.
"After that, it became mind over matter, and he progressed incredibly."
Salazar wanted it understood that Powell is Centrowitz's coach. Once Centrowitz was able to run, Powell designed the workouts.
Still, Salazar took quiet satisfaction in watching Centrowitz battle his way onto the U.S. Olympic Team Sunday at Hayward Field.
Said Salazar: "He has tons of guts."